cc: The recent texture manager bug uncovered some unnecessary code

cc/prioritized_texture.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "cc/prioritized_texture.h"
 
 #include "cc/platform_color.h"
 #include "cc/prioritized_texture_manager.h"
@@ skipping 178 matching lines @@
 }
 
 void PrioritizedTexture::Backing::updateInDrawingImplTree()
 {
     DCHECK(Proxy::isImplThread() && Proxy::isMainThreadBlocked());
     m_inDrawingImplTree = !!owner();
     if (!m_inDrawingImplTree)
         DCHECK(m_priorityAtLastPriorityUpdate == PriorityCalculator::lowestPriority());
 }
 
+void PrioritizedTexture::returnBackingTexture()
+{
+    DCHECK(m_manager || !m_backing);
+    if (m_manager)
+        m_manager->returnBackingTexture(this);
+}
+
 } // namespace cc