This changes the signature of SkImageFilter::filterImageGPU() to use SkBitmaps for...

This changes the signature of SkImageFilter::filterImageGPU() to use SkBitmaps for input and output, and removes the rect param.  This allows us to return textures which are larger than the actual result, such as when GrAutoScratchTextures are used.  The SkBitmap's size represents the active region, while the GrTexture's size is the full texture size.

This fixes the bicubic image filter GM on the GPU, which otherwise draws garbage outside the filtered region.  It also moves us closer to unifying the signatures of SkImageFilter::onFilterImage() and SkImageFilter::filterImageGPU().

Review URL: https://codereview.appspot.com/7180048

git-svn-id: http://skia.googlecode.com/svn/trunk@7467 2bbb7eff-a529-9590-31e7-b0007b416f81