WebGL: Free temporary GPU resources held by inactive or hidden WebGL.

Source/platform/graphics/gpu/DrawingBufferTest.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 339 matching lines @@
     EXPECT_EQ(waitSyncPoint, webContext()->mostRecentlyWaitedSyncPoint());
 
     m_drawingBuffer->beginDestruction();
     waitSyncPoint = webContext()->insertSyncPoint();
     mailbox.syncPoint = waitSyncPoint;
     m_drawingBuffer->mailboxReleased(mailbox);
     // m_drawingBuffer waits for the sync point because the destruction is in progress.
     EXPECT_EQ(waitSyncPoint, webContext()->mostRecentlyWaitedSyncPoint());
 }
 
+TEST_F(DrawingBufferTest, verifySetIsHiddenProperlyAffectsMailboxes)
+{
+    blink::WebExternalTextureMailbox mailbox;
+
+    // Produce mailboxes.
+    m_drawingBuffer->markContentsChanged();
+    EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
+
+    unsigned waitSyncPoint = webContext()->insertSyncPoint();
+    mailbox.syncPoint = waitSyncPoint;
+    m_drawingBuffer->setIsHidden(true);
+    m_drawingBuffer->mailboxReleased(mailbox);
+    // m_drawingBuffer deletes mailbox immediately when hidden.
+    EXPECT_EQ(waitSyncPoint, webContext()->mostRecentlyWaitedSyncPoint());
+
+    // Fails to get mailbox when hidden.
+    EXPECT_FALSE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
+
+    m_drawingBuffer->beginDestruction();
+}
+
 } // namespace