Revert of Revert of Extract most of the mutable state of SkShader into a separate Context object. (https://codereview.chromium.org/249643002/)

Reason for revert:
Chromium side change landed along side DEPS roll that includes r14323.

Original issue's description:
> Revert of Extract most of the mutable state of SkShader into a separate Context object. (https://codereview.chromium.org/207683004/)
>
> Reason for revert:
> This is blocking the DEPS roll into Chromium. Failures can be seen here:
>
> http://build.chromium.org/p/tryserver.chromium/builders/android_dbg/builds/174333
>
> Original issue's description:
> > Extract most of the mutable state of SkShader into a separate Context object.
> >
> > SkShader currently stores some state during draw calls via setContext(...).
> > Move that mutable state into a separate SkShader::Context class that is
> > constructed on demand for the duration of the draw.
> >
> > Calls to setContext() are replaced with createContext() which returns a context
> > corresponding to the shader object or NULL if the parameters to createContext
> > are invalid.
> >
> > TEST=out/Debug/dm
> > BUG=skia:1976
> >
> > Committed: http://code.google.com/p/skia/source/detail?r=14216
> >
> > Committed: http://code.google.com/p/skia/source/detail?r=14323
>
> TBR=scroggo@google.com,skyostil@chromium.org,tomhudson@chromium.org,senorblanco@chromium.org,reed@google.com,bungeman@google.com,dominikg@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:1976
>
> Committed: http://code.google.com/p/skia/source/detail?r=14326

R=scroggo@google.com, skyostil@chromium.org, tomhudson@chromium.org, senorblanco@chromium.org, reed@google.com, bungeman@google.com, dominikg@chromium.org
TBR=bungeman@google.com, dominikg@chromium.org, reed@google.com, scroggo@google.com, senorblanco@chromium.org, skyostil@chromium.org, tomhudson@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=skia:1976

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/246403013

git-svn-id: http://skia.googlecode.com/svn/trunk@14328 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 29 insertions, 13 deletions

diff --git a/src/effects/SkTransparentShader.cpp b/src/effects/SkTransparentShader.cpp
index bd8b99a3c0..0997e62013 100644
--- a/src/effects/SkTransparentShader.cpp
+++ b/src/effects/SkTransparentShader.cpp
@@ -11,26 +11,40 @@
 #include "SkColorPriv.h"
 #include "SkString.h"
 
-bool SkTransparentShader::setContext(const SkBitmap& device,
-                                     const SkPaint& paint,
-                                     const SkMatrix& matrix) {
-    fDevice = &device;
-    fAlpha = paint.getAlpha();
+SkShader::Context* SkTransparentShader::createContext(const SkBitmap& device,
+                                                      const SkPaint& paint,
+                                                      const SkMatrix& matrix,
+                                                      void* storage) const {
+    if (!this->validContext(device, paint, matrix)) {
+        return NULL;
+    }
+
+    return SkNEW_PLACEMENT_ARGS(storage, TransparentShaderContext, (*this, device, paint, matrix));
+}
 
-    return this->INHERITED::setContext(device, paint, matrix);
+size_t SkTransparentShader::contextSize() const {
+    return sizeof(TransparentShaderContext);
 }
 
-uint32_t SkTransparentShader::getFlags() {
+SkTransparentShader::TransparentShaderContext::TransparentShaderContext(
+        const SkTransparentShader& shader, const SkBitmap& device,
+        const SkPaint& paint, const SkMatrix& matrix)
+    : INHERITED(shader, device, paint, matrix)
+    , fDevice(&device) {}
+
+SkTransparentShader::TransparentShaderContext::~TransparentShaderContext() {}
+
+uint32_t SkTransparentShader::TransparentShaderContext::getFlags() const {
     uint32_t flags = this->INHERITED::getFlags();
 
     switch (fDevice->colorType()) {
         case kRGB_565_SkColorType:
             flags |= kHasSpan16_Flag;
-            if (fAlpha == 255)
+            if (this->getPaintAlpha() == 255)
                 flags |= kOpaqueAlpha_Flag;
             break;
         case kN32_SkColorType:
-            if (fAlpha == 255 && fDevice->isOpaque())
+            if (this->getPaintAlpha() == 255 && fDevice->isOpaque())
                 flags |= kOpaqueAlpha_Flag;
             break;
         default:
@@ -39,8 +53,9 @@ uint32_t SkTransparentShader::getFlags() {
     return flags;
 }
 
-void SkTransparentShader::shadeSpan(int x, int y, SkPMColor span[], int count) {
-    unsigned scale = SkAlpha255To256(fAlpha);
+void SkTransparentShader::TransparentShaderContext::shadeSpan(int x, int y, SkPMColor span[],
+                                                              int count) {
+    unsigned scale = SkAlpha255To256(this->getPaintAlpha());
 
     switch (fDevice->colorType()) {
         case kN32_SkColorType:
@@ -63,7 +78,7 @@ void SkTransparentShader::shadeSpan(int x, int y, SkPMColor span[], int count) {
                     span[i] = SkPixel16ToPixel32(src[i]);
                 }
             } else {
-                unsigned alpha = fAlpha;
+                unsigned alpha = this->getPaintAlpha();
                 for (int i = count - 1; i >= 0; --i) {
                     uint16_t c = src[i];
                     unsigned r = SkPacked16ToR32(c);
@@ -97,7 +112,8 @@ void SkTransparentShader::shadeSpan(int x, int y, SkPMColor span[], int count) {
     }
 }
 
-void SkTransparentShader::shadeSpan16(int x, int y, uint16_t span[], int count) {
+void SkTransparentShader::TransparentShaderContext::shadeSpan16(int x, int y, uint16_t span[],
+                                                                int count) {
     SkASSERT(fDevice->colorType() == kRGB_565_SkColorType);
 
     uint16_t* src = fDevice->getAddr16(x, y);