When a surface is backed by an external render target force a copy on image snap

src/image/SkSurface_Gpu.cpp

Index: src/image/SkSurface_Gpu.cpp
diff --git a/src/image/SkSurface_Gpu.cpp b/src/image/SkSurface_Gpu.cpp
index 7d98b31af58f19d6f39f52278dfed35fe2b571d2..86b8f3a66123b65c1034ca8975565a6422cd908c 100644
--- a/src/image/SkSurface_Gpu.cpp
+++ b/src/image/SkSurface_Gpu.cpp
@@ -81,8 +81,7 @@ SkImage* SkSurface_Gpu::onNewImageSnapshot(Budgeted budgeted, ForceCopyMode forc
     SkASSERT(rt);
     GrTexture* tex = rt->asTexture();
     SkAutoTUnref<GrTexture> copy;

[robertphillips, 2016/02/24 13:11:54]

// When clients wrap an external FBO in a Surface we need to keep that resource
attached to the surface rather than passing it off to the snapped Image. This is
particularly relevant when the wrapped FBO is a hardware overlay.

?

[bsalomon, 2016/02/26 17:44:44]

Added a comment.

-    // TODO: Force a copy when the rt is an external resource.
-    if (kYes_ForceCopyMode == forceCopyMode || !tex) {
+    if (kYes_ForceCopyMode == forceCopyMode || !tex || rt->resourcePriv().isExternal()) {
         GrSurfaceDesc desc = fDevice->accessRenderTarget()->desc();
         GrContext* ctx = fDevice->context();
         desc.fFlags = desc.fFlags & !kRenderTarget_GrSurfaceFlag;