fix slowness of getImageData() for CanvasRenderingContext2D in linux due to un-optimized format for…

src/gpu/gl/GrGpuGL.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 
 #ifndef GrGpuGL_DEFINED
@@ skipping 26 matching lines @@
     GrGLBinding glBinding() const { return fGLContext.info().binding(); }
     GrGLVersion glVersion() const { return fGLContext.info().version(); }
     GrGLSLGeneration glslGeneration() const { return fGLContext.info().glslGeneration(); }
 
     // Used by GrGLProgram to bind necessary textures for GrGLEffects.
     void bindTexture(int unitIdx, const GrTextureParams& params, GrGLTexture* texture);
 
     bool programUnitTest(int maxStages);
 
     // GrGpu overrides
-    virtual GrPixelConfig preferredReadPixelsConfig(GrPixelConfig config) const SK_OVERRIDE;
-    virtual GrPixelConfig preferredWritePixelsConfig(GrPixelConfig config) const SK_OVERRIDE;
+    virtual GrPixelConfig preferredReadPixelsConfig(GrPixelConfig readConfig, GrPixelConfig targetConfig) const SK_OVERRIDE;
+    virtual GrPixelConfig preferredWritePixelsConfig(GrPixelConfig writeConfig, GrPixelConfig targetConfig) const SK_OVERRIDE;
     virtual bool canWriteTexturePixels(const GrTexture*, GrPixelConfig srcConfig) const SK_OVERRIDE;
     virtual bool readPixelsWillPayForYFlip(
                                     GrRenderTarget* renderTarget,
                                     int left, int top,
                                     int width, int height,
                                     GrPixelConfig config,
                                     size_t rowBytes) const SK_OVERRIDE;
     virtual bool fullReadPixelsIsFasterThanPartial() const SK_OVERRIDE;
 
     virtual void initCopySurfaceDstDesc(const GrSurface* src, GrTextureDesc* desc) SK_OVERRIDE;
@@ skipping 379 matching lines @@
     ///@}
 
     // we record what stencil format worked last time to hopefully exit early
     // from our loop that tries stencil formats and calls check fb status.
     int fLastSuccessfulStencilFmtIdx;
 
     typedef GrGpu INHERITED;
 };
 
 #endif