Change undefined SkGpuRenderTarget and SkGpuTexture forward declares to GrRenderTarget and GrTextur…

src/gpu/SkGrPixelRef.cpp

Index: src/gpu/SkGrPixelRef.cpp
diff --git a/src/gpu/SkGrPixelRef.cpp b/src/gpu/SkGrPixelRef.cpp
index 8751c5d8bf4e408959809bca842c6b0013fba1eb..98819bfd73a4fab9e5a3bf152f2fd068b264d92f 100644
--- a/src/gpu/SkGrPixelRef.cpp
+++ b/src/gpu/SkGrPixelRef.cpp
@@ -128,9 +128,9 @@ SkGrPixelRef::~SkGrPixelRef() {
     GrSafeUnref(fSurface);
 }
 
-SkGpuTexture* SkGrPixelRef::getTexture() {
+GrTexture* SkGrPixelRef::getTexture() {
     if (NULL != fSurface) {
-        return (SkGpuTexture*) fSurface->asTexture();
+        return fSurface->asTexture();
     }
     return NULL;
 }