Extract most of the mutable state of SkShader into a separate Context object.

src/core/SkPictureShader.h

Index: src/core/SkPictureShader.h
diff --git a/src/core/SkPictureShader.h b/src/core/SkPictureShader.h
index ea74b56d73d857394f9c20b227d41368f1623fa0..d1be0591824e27e1f28962b665c7f33ba40995af 100644
--- a/src/core/SkPictureShader.h
+++ b/src/core/SkPictureShader.h
@@ -24,13 +24,33 @@ public:
     static SkPictureShader* Create(SkPicture*, TileMode, TileMode);
     virtual ~SkPictureShader();
 
-    virtual bool setContext(const SkBitmap&, const SkPaint&, const SkMatrix&) SK_OVERRIDE;
-    virtual void endContext() SK_OVERRIDE;
-    virtual uint32_t getFlags() SK_OVERRIDE;
+    virtual bool validContext(const SkBitmap&, const SkPaint&,
+                              const SkMatrix&, SkMatrix* totalInverse = NULL) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(const SkBitmap& device, const SkPaint& paint,
+                                             const SkMatrix& matrix, void* storage) const
+            SK_OVERRIDE;
+    virtual size_t contextSize() 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;
+    class PictureShaderContext : public SkShader::Context {
+    public:
+        PictureShaderContext(const SkPictureShader& shader, const SkBitmap& device,
+                             const SkPaint& paint, const SkMatrix& matrix,
+                             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)
@@ -46,13 +66,18 @@ protected:
 private:
     SkPictureShader(SkPicture*, TileMode, TileMode);
 
-    bool buildBitmapShader(const SkMatrix&) const;
+    SkShader* validInternal(const SkBitmap& device, const SkPaint& paint,
+                            const SkMatrix& matrix, SkMatrix* totalInverse) const;
+
+    SkShader* refBitmapShader(const SkMatrix&) const;
 
     SkPicture*  fPicture;
     TileMode    fTmx, fTmy;
 
-    mutable SkAutoTUnref<SkShader>  fCachedShader;
+    mutable SkMutex                 fCachedBitmapShaderMutex;
+    mutable SkAutoTUnref<SkShader>  fCachedBitmapShader;
     mutable SkSize                  fCachedTileScale;
+    mutable SkMatrix                fCachedLocalMatrix;
 
     typedef SkShader INHERITED;
 };