[Oilpan] Migrate classes under module/webgl onto oilpan heap

Source/modules/webgl/CHROMIUMValuebuffer.cpp

 // Copyright (c) 2014 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 "modules/webgl/CHROMIUMValuebuffer.h"
 
 #include "modules/webgl/WebGLRenderingContextBase.h"
 
 namespace blink {
 
-PassRefPtrWillBeRawPtr<CHROMIUMValuebuffer> CHROMIUMValuebuffer::create(WebGLRenderingContextBase* ctx)
+CHROMIUMValuebuffer* CHROMIUMValuebuffer::create(WebGLRenderingContextBase* ctx)
 {
-    return adoptRefWillBeNoop(new CHROMIUMValuebuffer(ctx));
+    return new CHROMIUMValuebuffer(ctx);
 }
 
 CHROMIUMValuebuffer::~CHROMIUMValuebuffer()
 {
     // Always call detach here to ensure that platform object deletion
     // happens with Oilpan enabled. It keeps the code regular to do it
     // with or without Oilpan enabled.
     //
     // See comment in WebGLBuffer's destructor for additional
     // information on why this is done for WebGLSharedObject-derived
     // objects.
     detachAndDeleteObject();

[haraken, 2015/08/04 00:06:52]

Sigbjorn: I'm sorry for asking similar questions repeatedly, but help me
understand. detachAndDeleteObject() calls WebGLObject::getAWebGraphicsContext3D
and it touches WebGLObject::m_context, which is another on-heap object. Why is
it safe?

[sof, 2015/08/04 06:20:45]

It is safe because:

 - if m_context (WebGLRenderingContextBase) is finalized at the same time as
this WebGLSharedObject, it (m_context) will have been (eagerly) finalized first.
At which point it will have called detachAndRemoveAllObjects() to explicitly
detach this & other objects.
 - if m_context isn't finalized at the same time, detaching this object needs to
happen. Which is safe, as m_context is still alive.

[haraken, 2015/08/04 06:35:40]

Thanks, I'm now convinced. I'll try not to forget it :)

 }
 
 CHROMIUMValuebuffer::CHROMIUMValuebuffer(WebGLRenderingContextBase* ctx)
     : WebGLSharedPlatform3DObject(ctx)
     , m_hasEverBeenBound(false)
 {
     setObject(ctx->webContext()->createValuebufferCHROMIUM());
 }
 
 void CHROMIUMValuebuffer::deleteObjectImpl(WebGraphicsContext3D* context3d)
 {
     context3d->deleteValuebufferCHROMIUM(m_object);
     m_object = 0;
 }
 
 } // namespace blink