Don't copy image buffer when calculating size.

src/core/SkImageCacherator.cpp

Index: src/core/SkImageCacherator.cpp
diff --git a/src/core/SkImageCacherator.cpp b/src/core/SkImageCacherator.cpp
index 54045d5821367a8de692fa44d6ba44f865f6d3a4..1b32a4f707b74727fc68d3c243fa6f4254364754 100644
--- a/src/core/SkImageCacherator.cpp
+++ b/src/core/SkImageCacherator.cpp
@@ -157,6 +157,12 @@ bool SkImageCacherator::directGeneratePixels(const SkImageInfo& info, void* pixe
     return generator->getPixels(info, pixels, rb);
 }
 
+bool SkImageCacherator::canGenerateTexture(const GrContextThreadSafeProxy& proxy)
+{
+    ScopedGenerator generator(fSharedGenerator);
+    return generator->canGenerateTexture(proxy);
+}
+
 //////////////////////////////////////////////////////////////////////////////////////////////////
 
 bool SkImageCacherator::lockAsBitmapOnlyIfAlreadyCached(SkBitmap* bitmap) {