Add the method isOpaque() to SkImage

src/image/SkImage_Gpu.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkImagePriv.h"
 #include "SkBitmap.h"
@@ skipping 10 matching lines @@
     virtual ~SkImage_Gpu();
 
     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) SK_OVERRIDE;
     virtual void onDrawRectToRect(SkCanvas*, const SkRect* src, const SkRect& dst, const SkPaint*) SK_OVERRIDE;
     virtual GrTexture* onGetTexture() SK_OVERRIDE;
     virtual bool getROPixels(SkBitmap*) const SK_OVERRIDE;
 
     GrTexture* getTexture() { return fBitmap.getTexture(); }
 
     virtual SkShader* onNewShader(SkShader::TileMode, SkShader::TileMode) const SK_OVERRIDE;
+
+    virtual bool isOpaque() const SK_OVERRIDE;
 private:
     SkBitmap    fBitmap;
 
     typedef SkImage_Base INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage_Gpu::SkImage_Gpu(const SkBitmap& bitmap)
     : INHERITED(bitmap.width(), bitmap.height())
@@ skipping 32 matching lines @@
     if (NULL == bitmap.getTexture()) {
         return NULL;
     }
 
     return SkNEW_ARGS(SkImage_Gpu, (bitmap));
 }
 
 GrTexture* SkTextureImageGetTexture(SkImage* image) {
     return ((SkImage_Gpu*)image)->getTexture();
 }
+
+bool SkImage_Gpu::isOpaque() const {
+    return fBitmap.isOpaque();
+}