Move code to dump GrSurface as a png to helper files

src/gpu/GrLayerCache.cpp

Index: src/gpu/GrLayerCache.cpp
diff --git a/src/gpu/GrLayerCache.cpp b/src/gpu/GrLayerCache.cpp
index 7c2a8bd61c16bbc0e1d03dc4dcd967916e84e181..235020560a20aa32cae3d2fe151b5965201dab43 100644
--- a/src/gpu/GrLayerCache.cpp
+++ b/src/gpu/GrLayerCache.cpp
@@ -443,7 +443,7 @@ void GrLayerCache::writeLayersToDisk(const SkString& dirName) {
         SkString fileName(dirName);
         fileName.append("\\atlas.png");
 
-        atlasTexture->surfacePriv().savePixels(fileName.c_str());
+        SkSaveGrSurfacePixelsAsPNG(atlasTexture, fileName.c_str());
     }
 
     SkTDynamicHash<GrCachedLayer, GrCachedLayer::Key>::Iter iter(&fLayerHash);
@@ -461,7 +461,7 @@ void GrLayerCache::writeLayersToDisk(const SkString& dirName) {
         fileName.appendU32(layer->fKey.start());
         fileName.append(".png");
 
-        layer->texture()->surfacePriv().savePixels(fileName.c_str());
+        SkSaveGrSurfacePixelsAsPNG(layer->texture(), fileName.c_str());
     }
 }
 #endif