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

src/gpu/GrTexture.cpp

Index: src/gpu/GrTexture.cpp
diff --git a/src/gpu/GrTexture.cpp b/src/gpu/GrTexture.cpp
index e954c5ee85bdde547c9082643c23db473cce6dbe..b76075747889f2fea50194c6be486c221a5d2c0a 100644
--- a/src/gpu/GrTexture.cpp
+++ b/src/gpu/GrTexture.cpp
@@ -81,7 +81,7 @@ GrTexture::GrTexture(GrGpu* gpu, LifeCycle lifeCycle, const GrSurfaceDesc& desc)
     : INHERITED(gpu, lifeCycle, desc)
     , fMipMapsStatus(kNotAllocated_MipMapsStatus) {
 
-    if (kWrapped_LifeCycle != lifeCycle && !GrPixelConfigIsCompressed(desc.fConfig)) {
+    if (!this->isExternal() && !GrPixelConfigIsCompressed(desc.fConfig)) {
         GrScratchKey key;
         GrTexturePriv::ComputeScratchKey(desc, &key);
         this->setScratchKey(key);