Revert of Prefer to use the OES_depth24 extension for WebGL's depth-only back buffers.

third_party/WebKit/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 205 matching lines @@
         if (!drawingBuffer->initialize(size)) {
             drawingBuffer->beginDestruction();
             return PassRefPtr<DrawingBufferForTests>();
         }
         return drawingBuffer.release();
     }
 
     DrawingBufferForTests(PassOwnPtr<WebGraphicsContext3D> context,
         PassOwnPtr<Extensions3DUtil> extensionsUtil,
         PreserveDrawingBuffer preserve)
-        : DrawingBuffer(context, extensionsUtil, DrawingBuffer::SupportedExtensions(), preserve, WebGraphicsContext3D::Attributes())
+        : DrawingBuffer(context, extensionsUtil, false /* multisampleExtensionSupported */,
+            false /* packedDepthStencilExtensionSupported */, false /* discardFramebufferSupported */, preserve, WebGraphicsContext3D::Attributes())
         , m_live(0)
     { }
 
     ~DrawingBufferForTests() override
     {
         if (m_live)
             *m_live = false;
     }
 
     bool* m_live;
@@ skipping 498 matching lines @@
     m_drawingBuffer->markContentsChanged();
     EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
     EXPECT_EQ(initialSize, webContext()->mostRecentlyProducedSize());
     EXPECT_FALSE(mailbox.allowOverlay);
 
     m_drawingBuffer->mailboxReleased(mailbox, false);
     m_drawingBuffer->beginDestruction();
 }
 
 } // namespace blink