Cache render targets that render to wrapped textures

src/gpu/gl/GrGLTextureRenderTarget.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLTextureRenderTarget.h"
 
 #include "SkTraceMemoryDump.h"
@@ skipping 19 matching lines @@
   if (this->isPurgeable()) {
     traceMemoryDump->dumpNumericValue(dumpName.c_str(), "purgeable_size",
                                       "bytes", size);
   }
 
   SkString texture_id;
   texture_id.appendU32(this->textureID());
   traceMemoryDump->setMemoryBacking(dumpName.c_str(), "gl_texture",
                                     texture_id.c_str());
 }
+
+bool GrGLTextureRenderTarget::refsWrappedResources() const {
+    // The GrGLRenderTarget part of this class will not reference external resources, because client
+    // provides either an external texture or an external fbo, never both. The external texture
+    // produces GrGLTextureRenderTarget, the external fbo produces plain GrGLRenderTarget.o
+    return this->GrGLTexture::refsWrappedResources();
+}