WebGL: Don't destroy mailbox textures in the destructor until they're released.

Source/web/tests/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 94 matching lines @@
 static const int initialHeight = 100;
 static const int alternateHeight = 50;
 
 } // namespace
 
 class DrawingBufferTest : public Test {
 protected:
     virtual void SetUp()
     {
         RefPtr<FakeContextEvictionManager> contextEvictionManager = adoptRef(new FakeContextEvictionManager());
-        m_context = adoptPtr(new WebGraphicsContext3DForTests);
-        m_drawingBuffer = DrawingBuffer::create(m_context.get(), IntSize(initialWidth, initialHeight), DrawingBuffer::Preserve, contextEvictionManager.release());
+        OwnPtr<WebGraphicsContext3DForTests> context = adoptPtr(new WebGraphicsContext3DForTests);
+        m_context = context.get();
+        m_drawingBuffer = DrawingBuffer::create(context.release(), IntSize(initialWidth, initialHeight), DrawingBuffer::Preserve, contextEvictionManager.release());
     }
 
     WebGraphicsContext3DForTests* webContext()
     {
-        return m_context.get();
+        return m_context;
     }
 
-    OwnPtr<WebGraphicsContext3DForTests> m_context;
+    WebGraphicsContext3DForTests* m_context;
     RefPtr<DrawingBuffer> m_drawingBuffer;
 };
 
 namespace {
 
 TEST_F(DrawingBufferTest, testPaintRenderingResultsToCanvas)
 {
     OwnPtr<ImageBufferSurface> imageBufferSurface = adoptPtr(new UnacceleratedImageBufferSurface(IntSize(initialWidth, initialHeight)));
     EXPECT_FALSE(!imageBufferSurface);
     EXPECT_TRUE(imageBufferSurface->isValid());
@@ skipping 93 matching lines @@
     EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&recycledMailbox, 0));
     EXPECT_EQ(TextureMailboxWrapper(mailbox3), TextureMailboxWrapper(recycledMailbox));
 
     // The third recycled mailbox must be 1.
     m_drawingBuffer->markContentsChanged();
     EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&recycledMailbox, 0));
     EXPECT_EQ(TextureMailboxWrapper(mailbox1), TextureMailboxWrapper(recycledMailbox));
 }
 
 } // namespace