Add the method isOpaque() to SkImage

src/image/SkImage_Gpu.cpp

Index: src/image/SkImage_Gpu.cpp
diff --git a/src/image/SkImage_Gpu.cpp b/src/image/SkImage_Gpu.cpp
index 7a73c7453bc918ccf0ceb7f4e41ae02ea643e879..9b9f4b1f75338a0f90d77b87aba3de81474bfaae 100644
--- a/src/image/SkImage_Gpu.cpp
+++ b/src/image/SkImage_Gpu.cpp
@@ -28,6 +28,8 @@ public:
     GrTexture* getTexture() { return fBitmap.getTexture(); }
 
     virtual SkShader* onNewShader(SkShader::TileMode, SkShader::TileMode) const SK_OVERRIDE;
+
+    virtual bool isOpaque() const SK_OVERRIDE;
 private:
     SkBitmap    fBitmap;
 
@@ -80,3 +82,7 @@ SkImage* SkImage::NewTexture(const SkBitmap& bitmap) {
 GrTexture* SkTextureImageGetTexture(SkImage* image) {
     return ((SkImage_Gpu*)image)->getTexture();
 }
+
+bool SkImage_Gpu::isOpaque() const {
+    return fBitmap.isOpaque();
+}