Use SkShader's localMat for SkLocalMatrixShader.

Instead of setting SkShader::fLocalMatrix to Identity and storing
a separate SkMatrix inside SkLocalMatrixShader, reuse
SkShader::fLocalMatrix.

R=reed@google.com

Author: scroggo@google.com

Review URL: https://codereview.chromium.org/386693003

3 files changed, 13 insertions, 2 deletions

diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index ca26eb4496..03d983fe58 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -231,13 +231,14 @@ private:
     // V27: Remove SkUnitMapper from gradients (and skia).
     // V28: No longer call bitmap::flatten inside SkWriteBuffer::writeBitmap.
     // V29: Removed SaveFlags parameter from save().
+    // V30: Remove redundant SkMatrix from SkLocalMatrixShader.
 
     // Note: If the picture version needs to be increased then please follow the
     // steps to generate new SKPs in (only accessible to Googlers): http://goo.gl/qATVcw
 
     // Only SKPs within the min/current picture version range (inclusive) can be read.
     static const uint32_t MIN_PICTURE_VERSION = 19;
-    static const uint32_t CURRENT_PICTURE_VERSION = 29;
+    static const uint32_t CURRENT_PICTURE_VERSION = 30;
 
     mutable uint32_t      fUniqueID;
 
diff --git a/include/core/SkReadBuffer.h b/include/core/SkReadBuffer.h
index 5db86345ad..faf7eb81a5 100644
--- a/include/core/SkReadBuffer.h
+++ b/include/core/SkReadBuffer.h
@@ -45,6 +45,7 @@ public:
         kColorShaderNoBool_Version         = 26,
         kNoUnitMappers_Version             = 27,
         kNoMoreBitmapFlatten_Version       = 28,
+        kSimplifyLocalMatrix_Version       = 30,
     };
 
     /**
diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index 8871f1b021..33a7a15b0f 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -41,11 +41,17 @@ public:
 
     /**
      *  Returns the local matrix.
+     *
+     *  FIXME: This can be incorrect for a Shader with its own local matrix
+     *  that is also wrapped via CreateLocalMatrixShader.
      */
     const SkMatrix& getLocalMatrix() const { return fLocalMatrix; }
 
     /**
      *  Returns true if the local matrix is not an identity matrix.
+     *
+     *  FIXME: This can be incorrect for a Shader with its own local matrix
+     *  that is also wrapped via CreateLocalMatrixShader.
      */
     bool hasLocalMatrix() const { return !fLocalMatrix.isIdentity(); }
 
@@ -474,7 +480,10 @@ protected:
 
 private:
     SkMatrix fLocalMatrix;
-    
+
+    // So the SkLocalMatrixShader can whack fLocalMatrix in its SkReadBuffer constructor.
+    friend class SkLocalMatrixShader;
+
     typedef SkFlattenable INHERITED;
 };