Remove SkShader virtual method validContext

patch from issue 267923005

BUG=skia:
R=scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/261773005

git-svn-id: http://skia.googlecode.com/svn/trunk@14573 2bbb7eff-a529-9590-31e7-b0007b416f81

10 files changed, 116 insertions, 168 deletions

diff --git a/src/core/SkBitmapProcShader.cpp b/src/core/SkBitmapProcShader.cpp
index 46cf7db136..503269ac10 100644
--- a/src/core/SkBitmapProcShader.cpp
+++ b/src/core/SkBitmapProcShader.cpp
@@ -97,39 +97,25 @@ static bool valid_for_drawing(const SkBitmap& bm) {
     return true;
 }
 
-bool SkBitmapProcShader::validInternal(const ContextRec& rec, SkMatrix* totalInverse,
-                                       SkBitmapProcState* state) const {
+SkShader::Context* SkBitmapProcShader::onCreateContext(const ContextRec& rec, void* storage) const {
     if (!fRawBitmap.getTexture() && !valid_for_drawing(fRawBitmap)) {
-        return false;
-    }
-
-    // Make sure we can use totalInverse as a cache.
-    SkMatrix totalInverseLocal;
-    if (NULL == totalInverse) {
-        totalInverse = &totalInverseLocal;
+        return NULL;
     }
-
+    
+    SkMatrix totalInverse;
     // Do this first, so we know the matrix can be inverted.
-    if (!this->INHERITED::validContext(rec, totalInverse)) {
-        return false;
+    if (!this->computeTotalInverse(rec, &totalInverse)) {
+        return NULL;
     }
+    
+    void* stateStorage = (char*)storage + sizeof(BitmapProcShaderContext);
+    SkBitmapProcState* state = SkNEW_PLACEMENT(stateStorage, SkBitmapProcState);
 
     SkASSERT(state);
     state->fTileModeX = fTileModeX;
     state->fTileModeY = fTileModeY;
     state->fOrigBitmap = fRawBitmap;
-    return state->chooseProcs(*totalInverse, *rec.fPaint);
-}
-
-bool SkBitmapProcShader::validContext(const ContextRec& rec, SkMatrix* totalInverse) const {
-    SkBitmapProcState state;
-    return this->validInternal(rec, totalInverse, &state);
-}
-
-SkShader::Context* SkBitmapProcShader::createContext(const ContextRec& rec, void* storage) const {
-    void* stateStorage = (char*)storage + sizeof(BitmapProcShaderContext);
-    SkBitmapProcState* state = SkNEW_PLACEMENT(stateStorage, SkBitmapProcState);
-    if (!this->validInternal(rec, NULL, state)) {
+    if (!state->chooseProcs(totalInverse, *rec.fPaint)) {
         state->~SkBitmapProcState();
         return NULL;
     }
diff --git a/src/core/SkBitmapProcShader.h b/src/core/SkBitmapProcShader.h
index e32d35e20d..0a036d3189 100644
--- a/src/core/SkBitmapProcShader.h
+++ b/src/core/SkBitmapProcShader.h
@@ -23,8 +23,6 @@ public:
     virtual bool isOpaque() const SK_OVERRIDE;
     virtual BitmapType asABitmap(SkBitmap*, SkMatrix*, TileMode*) const SK_OVERRIDE;
 
-    virtual bool validContext(const ContextRec&, SkMatrix* totalInverse) const SK_OVERRIDE;
-    virtual SkShader::Context* createContext(const ContextRec&, void* storage) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
     static bool CanDo(const SkBitmap&, TileMode tx, TileMode ty);
@@ -59,13 +57,12 @@ public:
 protected:
     SkBitmapProcShader(SkReadBuffer& );
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
+    virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE;
 
     SkBitmap    fRawBitmap;   // experimental for RLE encoding
     uint8_t     fTileModeX, fTileModeY;
 
 private:
-    bool validInternal(const ContextRec&, SkMatrix* totalInverse, SkBitmapProcState*) const;
-
     typedef SkShader INHERITED;
 };
 
diff --git a/src/core/SkBlitter.cpp b/src/core/SkBlitter.cpp
index 74cd29824e..0e12a627d0 100644
--- a/src/core/SkBlitter.cpp
+++ b/src/core/SkBlitter.cpp
@@ -591,29 +591,14 @@ public:
         return size;
     }
 
-    virtual bool validContext(const ContextRec& rec, SkMatrix* totalInverse) const SK_OVERRIDE {
-        if (!this->INHERITED::validContext(rec, totalInverse)) {
-            return false;
-        }
-        if (fProxy) {
-            return fProxy->validContext(rec);
-        }
-        return true;
-    }
-
-    virtual SkShader::Context* createContext(const ContextRec& rec, void* storage) const SK_OVERRIDE
-    {
-        if (!this->validContext(rec, NULL)) {
-            return NULL;
-        }
-
-        SkShader::Context* proxyContext;
+    virtual Context* onCreateContext(const ContextRec& rec, void* storage) const SK_OVERRIDE {
+        SkShader::Context* proxyContext = NULL;
         if (fProxy) {
             char* proxyContextStorage = (char*) storage + sizeof(Sk3DShaderContext);
             proxyContext = fProxy->createContext(rec, proxyContextStorage);
-            SkASSERT(proxyContext);
-        } else {
-            proxyContext = NULL;
+            if (!proxyContext) {
+                return NULL;
+            }
         }
         return SkNEW_PLACEMENT_ARGS(storage, Sk3DShaderContext, (*this, rec, proxyContext));
     }
@@ -1016,6 +1001,19 @@ const uint32_t gMask_00FF00FF = 0xFF00FF;
 
 ///////////////////////////////////////////////////////////////////////////////
 
+class SkTransparentShaderContext : public SkShader::Context {
+public:
+    SkTransparentShaderContext(const SkShader& shader, const SkShader::ContextRec& rec)
+        : INHERITED(shader, rec) {}
+
+    virtual void shadeSpan(int x, int y, SkPMColor colors[], int count) SK_OVERRIDE {
+        sk_bzero(colors, count * sizeof(SkPMColor));
+    }
+
+private:
+    typedef SkShader::Context INHERITED;
+};
+
 SkShaderBlitter::SkShaderBlitter(const SkBitmap& device, const SkPaint& paint,
                                  SkShader::Context* shaderContext)
         : INHERITED(device)
@@ -1035,9 +1033,6 @@ SkShaderBlitter::~SkShaderBlitter() {
 bool SkShaderBlitter::resetShaderContext(const SkBitmap& device, const SkPaint& paint,
                                          const SkMatrix& matrix) {
     SkShader::ContextRec rec(device, paint, matrix);
-    if (!fShader->validContext(rec)) {
-        return false;
-    }
 
     // Only destroy the old context if we have a new one. We need to ensure to have a
     // live context in fShaderContext because the storage is owned by an SkSmallAllocator
@@ -1045,8 +1040,11 @@ bool SkShaderBlitter::resetShaderContext(const SkBitmap& device, const SkPaint&
     // The new context will be of the same size as the old one because we use the same
     // shader to create it. It is therefore safe to re-use the storage.
     fShaderContext->~Context();
-    fShaderContext = fShader->createContext(rec, (void*)fShaderContext);
-    SkASSERT(fShaderContext);
-
-    return true;
+    SkShader::Context* ctx = fShader->createContext(rec, (void*)fShaderContext);
+    if (NULL == ctx) {
+        // Need a valid context in fShaderContext's storage, so we can later (or our caller) call
+        // the in-place destructor.
+        SkNEW_PLACEMENT_ARGS(fShaderContext, SkTransparentShaderContext, (*fShader, rec));
+    }
+    return ctx != NULL;
 }
diff --git a/src/core/SkComposeShader.cpp b/src/core/SkComposeShader.cpp
index 28511e3e8b..7a7dce66a0 100644
--- a/src/core/SkComposeShader.cpp
+++ b/src/core/SkComposeShader.cpp
@@ -73,33 +73,13 @@ void SkComposeShader::flatten(SkWriteBuffer& buffer) const {
     buffer.writeFlattenable(fMode);
 }
 
-/*  We call validContext/createContext on our two worker shaders.
-    However, we always let them see opaque alpha, and if the paint
-    really is translucent, then we apply that after the fact.
-
- */
-bool SkComposeShader::validContext(const ContextRec& rec, SkMatrix* totalInverse) const {
-    if (!this->INHERITED::validContext(rec, totalInverse)) {
-        return false;
+template <typename T> void safe_call_destructor(T* obj) {
+    if (obj) {
+        obj->~T();
     }
-
-    // we preconcat our localMatrix (if any) with the device matrix
-    // before calling our sub-shaders
-
-    SkMatrix tmpM;
-    tmpM.setConcat(*rec.fMatrix, this->getLocalMatrix());
-
-    ContextRec newRec(rec);
-    newRec.fMatrix = &tmpM;
-
-    return fShaderA->validContext(newRec) && fShaderB->validContext(newRec);
 }
 
-SkShader::Context* SkComposeShader::createContext(const ContextRec& rec, void* storage) const {
-    if (!this->validContext(rec)) {
-        return NULL;
-    }
-
+SkShader::Context* SkComposeShader::onCreateContext(const ContextRec& rec, void* storage) const {
     char* aStorage = (char*) storage + sizeof(ComposeShaderContext);
     char* bStorage = aStorage + fShaderA->contextSize();
 
@@ -120,11 +100,11 @@ SkShader::Context* SkComposeShader::createContext(const ContextRec& rec, void* s
 
     SkShader::Context* contextA = fShaderA->createContext(newRec, aStorage);
     SkShader::Context* contextB = fShaderB->createContext(newRec, bStorage);
-
-    // Both functions must succeed; otherwise validContext should have returned
-    // false.
-    SkASSERT(contextA);
-    SkASSERT(contextB);
+    if (!contextA || !contextB) {
+        safe_call_destructor(contextA);
+        safe_call_destructor(contextB);
+        return NULL;
+    }
 
     return SkNEW_PLACEMENT_ARGS(storage, ComposeShaderContext, (*this, rec, contextA, contextB));
 }
diff --git a/src/core/SkDraw.cpp b/src/core/SkDraw.cpp
index c4f5f74eef..a74e3c0f79 100644
--- a/src/core/SkDraw.cpp
+++ b/src/core/SkDraw.cpp
@@ -2353,7 +2353,6 @@ class SkTriColorShader : public SkShader {
 public:
     SkTriColorShader() {}
 
-    virtual SkShader::Context* createContext(const ContextRec&, void*) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
     class TriColorShaderContext : public SkShader::Context {
@@ -2378,18 +2377,14 @@ public:
 protected:
     SkTriColorShader(SkReadBuffer& buffer) : SkShader(buffer) {}
 
+    virtual Context* onCreateContext(const ContextRec& rec, void* storage) const SK_OVERRIDE {
+        return SkNEW_PLACEMENT_ARGS(storage, TriColorShaderContext, (*this, rec));
+    }
+
 private:
     typedef SkShader INHERITED;
 };
 
-SkShader::Context* SkTriColorShader::createContext(const ContextRec& rec, void* storage) const {
-    if (!this->validContext(rec)) {
-        return NULL;
-    }
-
-    return SkNEW_PLACEMENT_ARGS(storage, TriColorShaderContext, (*this, rec));
-}
-
 bool SkTriColorShader::TriColorShaderContext::setup(const SkPoint pts[], const SkColor colors[],
                                                     int index0, int index1, int index2) {
 
diff --git a/src/core/SkFilterShader.cpp b/src/core/SkFilterShader.cpp
index f1cc68d028..5094706ea7 100644
--- a/src/core/SkFilterShader.cpp
+++ b/src/core/SkFilterShader.cpp
@@ -55,11 +55,7 @@ uint32_t SkFilterShader::FilterShaderContext::getFlags() const {
     return shaderF;
 }
 
-SkShader::Context* SkFilterShader::createContext(const ContextRec& rec, void* storage) const {
-    if (!this->validContext(rec, NULL)) {
-        return NULL;
-    }
-
+SkShader::Context* SkFilterShader::onCreateContext(const ContextRec& rec, void* storage) const {
     char* shaderContextStorage = (char*)storage + sizeof(FilterShaderContext);
     SkShader::Context* shaderContext = fShader->createContext(rec, shaderContextStorage);
     SkASSERT(shaderContext);
@@ -71,10 +67,6 @@ size_t SkFilterShader::contextSize() const {
     return sizeof(FilterShaderContext) + fShader->contextSize();
 }
 
-bool SkFilterShader::validContext(const ContextRec& rec, SkMatrix* totalInverse) const {
-    return this->INHERITED::validContext(rec, totalInverse) && fShader->validContext(rec);
-}
-
 SkFilterShader::FilterShaderContext::FilterShaderContext(const SkFilterShader& filterShader,
                                                          SkShader::Context* shaderContext,
                                                          const ContextRec& rec)
diff --git a/src/core/SkFilterShader.h b/src/core/SkFilterShader.h
index 629f3f8c9e..3f983e26d9 100644
--- a/src/core/SkFilterShader.h
+++ b/src/core/SkFilterShader.h
@@ -17,8 +17,6 @@ public:
     SkFilterShader(SkShader* shader, SkColorFilter* filter);
     virtual ~SkFilterShader();
 
-    virtual bool validContext(const ContextRec&, SkMatrix* totalInverse) const SK_OVERRIDE;
-    virtual SkShader::Context* createContext(const ContextRec&, void* storage) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
     class FilterShaderContext : public SkShader::Context {
@@ -44,6 +42,8 @@ public:
 protected:
     SkFilterShader(SkReadBuffer& );
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
+    virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE;
+    
 
 private:
     SkShader*       fShader;
diff --git a/src/core/SkPictureShader.cpp b/src/core/SkPictureShader.cpp
index 81f9242854..9555624ffe 100644
--- a/src/core/SkPictureShader.cpp
+++ b/src/core/SkPictureShader.cpp
@@ -110,58 +110,55 @@ SkShader* SkPictureShader::refBitmapShader(const SkMatrix& matrix) const {
     return fCachedBitmapShader;
 }
 
-SkShader* SkPictureShader::validInternal(const ContextRec& rec, SkMatrix* totalInverse) const {
-    if (!this->INHERITED::validContext(rec, totalInverse)) {
-        return NULL;
-    }
+size_t SkPictureShader::contextSize() const {
+    return sizeof(PictureShaderContext);
+}
 
+SkShader::Context* SkPictureShader::onCreateContext(const ContextRec& rec, void* storage) const {
     SkAutoTUnref<SkShader> bitmapShader(this->refBitmapShader(*rec.fMatrix));
-    if (!bitmapShader || !bitmapShader->validContext(rec)) {
+    if (NULL == bitmapShader.get()) {
         return NULL;
     }
-
-    return bitmapShader.detach();
+    return PictureShaderContext::Create(storage, *this, rec, bitmapShader.detach());
 }
 
-bool SkPictureShader::validContext(const ContextRec& rec, SkMatrix* totalInverse) const {
-    SkAutoTUnref<SkShader> shader(this->validInternal(rec, totalInverse));
-    return shader != NULL;
-}
+/////////////////////////////////////////////////////////////////////////////////////////
 
-SkShader::Context* SkPictureShader::createContext(const ContextRec& rec, void* storage) const {
-    SkAutoTUnref<SkShader> bitmapShader(this->validInternal(rec, NULL));
-    if (!bitmapShader) {
-        return NULL;
+SkShader::Context* SkPictureShader::PictureShaderContext::Create(void* storage,
+                   const SkPictureShader& shader, const ContextRec& rec, SkShader* bitmapShader) {
+    PictureShaderContext* ctx = SkNEW_PLACEMENT_ARGS(storage, PictureShaderContext,
+                                                     (shader, rec, bitmapShader));
+    if (NULL == ctx->fBitmapShaderContext) {
+        ctx->~PictureShaderContext();
+        ctx = NULL;
     }
-
-    return SkNEW_PLACEMENT_ARGS(storage, PictureShaderContext, (*this, rec, bitmapShader.detach()));
-}
-
-size_t SkPictureShader::contextSize() const {
-    return sizeof(PictureShaderContext);
+    return ctx;
 }
 
 SkPictureShader::PictureShaderContext::PictureShaderContext(
         const SkPictureShader& shader, const ContextRec& rec, SkShader* bitmapShader)
     : INHERITED(shader, rec)
-    , fBitmapShader(bitmapShader)
+    , fBitmapShader(SkRef(bitmapShader))
 {
-    SkASSERT(fBitmapShader);
-    fBitmapShaderContextStorage = sk_malloc_throw(fBitmapShader->contextSize());
-    fBitmapShaderContext = fBitmapShader->createContext(rec, fBitmapShaderContextStorage);
-    SkASSERT(fBitmapShaderContext);
+    fBitmapShaderContextStorage = sk_malloc_throw(bitmapShader->contextSize());
+    fBitmapShaderContext = bitmapShader->createContext(rec, fBitmapShaderContextStorage);
+    //if fBitmapShaderContext is null, we are invalid
 }
 
 SkPictureShader::PictureShaderContext::~PictureShaderContext() {
-    fBitmapShaderContext->~Context();
+    if (fBitmapShaderContext) {
+        fBitmapShaderContext->~Context();
+    }
     sk_free(fBitmapShaderContextStorage);
 }
 
 uint32_t SkPictureShader::PictureShaderContext::getFlags() const {
+    SkASSERT(fBitmapShaderContext);
     return fBitmapShaderContext->getFlags();
 }
 
 SkShader::Context::ShadeProc SkPictureShader::PictureShaderContext::asAShadeProc(void** ctx) {
+    SkASSERT(fBitmapShaderContext);
     return fBitmapShaderContext->asAShadeProc(ctx);
 }
 
diff --git a/src/core/SkPictureShader.h b/src/core/SkPictureShader.h
index 2ef6c1c92a..1788205558 100644
--- a/src/core/SkPictureShader.h
+++ b/src/core/SkPictureShader.h
@@ -24,29 +24,8 @@ public:
     static SkPictureShader* Create(SkPicture*, TileMode, TileMode, const SkMatrix* = NULL);
     virtual ~SkPictureShader();
 
-    virtual bool validContext(const ContextRec&, SkMatrix* totalInverse) const SK_OVERRIDE;
-    virtual SkShader::Context* createContext(const ContextRec&, void* storage) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
-    class PictureShaderContext : public SkShader::Context {
-    public:
-        PictureShaderContext(const SkPictureShader&, const ContextRec&, SkShader* bitmapShader);
-        virtual ~PictureShaderContext();
-
-        virtual uint32_t getFlags() const SK_OVERRIDE;
-
-        virtual ShadeProc asAShadeProc(void** ctx) SK_OVERRIDE;
-        virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
-        virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count) SK_OVERRIDE;
-
-    private:
-        SkAutoTUnref<SkShader>  fBitmapShader;
-        SkShader::Context*      fBitmapShaderContext;
-        void*                   fBitmapShaderContextStorage;
-
-        typedef SkShader::Context INHERITED;
-    };
-
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPictureShader)
 
@@ -57,11 +36,11 @@ public:
 protected:
     SkPictureShader(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
+    virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE;
 
 private:
     SkPictureShader(SkPicture*, TileMode, TileMode, const SkMatrix* = NULL);
 
-    SkShader* validInternal(const ContextRec&, SkMatrix* totalInverse) const;
     SkShader* refBitmapShader(const SkMatrix&) const;
 
     SkPicture*  fPicture;
@@ -72,6 +51,29 @@ private:
     mutable SkSize                  fCachedTileScale;
     mutable SkMatrix                fCachedLocalMatrix;
 
+    class PictureShaderContext : public SkShader::Context {
+    public:
+        static Context* Create(void* storage, const SkPictureShader&, const ContextRec&,
+                               SkShader* bitmapShader);
+
+        virtual ~PictureShaderContext();
+        
+        virtual uint32_t getFlags() const SK_OVERRIDE;
+        
+        virtual ShadeProc asAShadeProc(void** ctx) SK_OVERRIDE;
+        virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
+        virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count) SK_OVERRIDE;
+        
+    private:
+        PictureShaderContext(const SkPictureShader&, const ContextRec&, SkShader* bitmapShader);
+
+        SkAutoTUnref<SkShader>  fBitmapShader;
+        SkShader::Context*      fBitmapShaderContext;
+        void*                   fBitmapShaderContextStorage;
+        
+        typedef SkShader::Context INHERITED;
+    };
+    
     typedef SkShader INHERITED;
 };
 
diff --git a/src/core/SkShader.cpp b/src/core/SkShader.cpp
index 67dd581543..8e6112ae7d 100644
--- a/src/core/SkShader.cpp
+++ b/src/core/SkShader.cpp
@@ -6,6 +6,7 @@
  */
 
 #include "SkBitmapProcShader.h"
+#include "SkEmptyShader.h"
 #include "SkReadBuffer.h"
 #include "SkMallocPixelRef.h"
 #include "SkPaint.h"
@@ -44,23 +45,25 @@ void SkShader::flatten(SkWriteBuffer& buffer) const {
     }
 }
 
-bool SkShader::computeTotalInverse(const SkMatrix& matrix, SkMatrix* totalInverse) const {
-    const SkMatrix* m = &matrix;
+bool SkShader::computeTotalInverse(const ContextRec& rec, SkMatrix* totalInverse) const {
+    const SkMatrix* m = rec.fMatrix;
     SkMatrix        total;
 
     if (this->hasLocalMatrix()) {
-        total.setConcat(matrix, this->getLocalMatrix());
+        total.setConcat(*m, this->getLocalMatrix());
         m = &total;
     }
-
     return m->invert(totalInverse);
 }
 
-bool SkShader::validContext(const ContextRec& rec, SkMatrix* totalInverse) const {
-    return this->computeTotalInverse(*rec.fMatrix, totalInverse);
+SkShader::Context* SkShader::createContext(const ContextRec& rec, void* storage) const {
+    if (!this->computeTotalInverse(rec, NULL)) {
+        return NULL;
+    }
+    return this->onCreateContext(rec, storage);
 }
 
-SkShader::Context* SkShader::createContext(const ContextRec&, void* storage) const {
+SkShader::Context* SkShader::onCreateContext(const ContextRec&, void*) const {
     return NULL;
 }
 
@@ -71,11 +74,9 @@ size_t SkShader::contextSize() const {
 SkShader::Context::Context(const SkShader& shader, const ContextRec& rec)
     : fShader(shader)
 {
-    SkASSERT(fShader.validContext(rec));
-
     // Because the context parameters must be valid at this point, we know that the matrix is
     // invertible.
-    SkAssertResult(fShader.computeTotalInverse(*rec.fMatrix, &fTotalInverse));
+    SkAssertResult(fShader.computeTotalInverse(rec, &fTotalInverse));
     fTotalInverseClass = (uint8_t)ComputeMatrixClass(fTotalInverse);
 
     fPaintAlpha = rec.fPaint->getAlpha();
@@ -188,6 +189,10 @@ GrEffectRef* SkShader::asNewEffect(GrContext*, const SkPaint&) const {
     return NULL;
 }
 
+SkShader* SkShader::CreateEmptyShader() {
+    return SkNEW(SkEmptyShader);
+}
+
 SkShader* SkShader::CreateBitmapShader(const SkBitmap& src, TileMode tmx, TileMode tmy,
                                        const SkMatrix* localMatrix) {
     return ::CreateBitmapShader(src, tmx, tmy, localMatrix, NULL);
@@ -246,11 +251,7 @@ uint8_t SkColorShader::ColorShaderContext::getSpan16Alpha() const {
     return SkGetPackedA32(fPMColor);
 }
 
-SkShader::Context* SkColorShader::createContext(const ContextRec& rec, void* storage) const {
-    if (!this->validContext(rec)) {
-        return NULL;
-    }
-
+SkShader::Context* SkColorShader::onCreateContext(const ContextRec& rec, void* storage) const {
     return SkNEW_PLACEMENT_ARGS(storage, ColorShaderContext, (*this, rec));
 }