Add support for creating texture backed images where Skia will delete the texture.

src/gpu/GrGpuResource.cpp

Index: src/gpu/GrGpuResource.cpp
diff --git a/src/gpu/GrGpuResource.cpp b/src/gpu/GrGpuResource.cpp
index c2d93620d5df3a7d06c6ef444a29bcd22b171afa..49212df416d8d639b143e7580fd9f507d33e2395 100644
--- a/src/gpu/GrGpuResource.cpp
+++ b/src/gpu/GrGpuResource.cpp
@@ -145,7 +145,7 @@ void GrGpuResource::setScratchKey(const GrScratchKey& scratchKey) {
     SkASSERT(!fScratchKey.isValid());
     SkASSERT(scratchKey.isValid());
     // Wrapped resources can never have a scratch key.
-    if (this->isWrapped()) {
+    if (this->cacheAccess().isExternal()) {
         return;
     }
     fScratchKey = scratchKey;