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

src/gpu/GrGpuResourcePriv.h

 
 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGpuResourcePriv_DEFINED
 #define GrGpuResourcePriv_DEFINED
@@ skipping 32 matching lines @@
 
     /**
      * Does the resource count against the resource budget?
      */
     SkBudgeted isBudgeted() const {
         bool ret = GrGpuResource::kCached_LifeCycle == fResource->fLifeCycle;
         SkASSERT(ret || !fResource->getUniqueKey().isValid());
         return SkBudgeted(ret);
     }
 
-    /** 
+    /**
+     * Is the resource object wrapping an externally allocated GPU resource?
+     */
+    bool isExternal() const { return fResource->isExternal(); }
+
+    /**
      * If this resource can be used as a scratch resource this returns a valid scratch key.
      * Otherwise it returns a key for which isNullScratch is true. The resource may currently be
      * used as a uniquely keyed resource rather than scratch. Check isScratch().
      */
     const GrScratchKey& getScratchKey() const { return fResource->fScratchKey; }
 
     /**
      * If the resource has a scratch key, the key will be removed. Since scratch keys are installed
      * at resource creation time, this means the resource will never again be used as scratch.
      */
@@ skipping 13 matching lines @@
     friend class GrGpuResource; // to construct/copy this type.
 };
 
 inline GrGpuResource::ResourcePriv GrGpuResource::resourcePriv() { return ResourcePriv(this); }
 
 inline const GrGpuResource::ResourcePriv GrGpuResource::resourcePriv() const {
     return ResourcePriv(const_cast<GrGpuResource*>(this));
 }
 
 #endif