[Oilpan] Remove a GC_PLUGIN_IGNORE

Source/modules/webgl/WebGLRenderingContextBase.h

 /*
  * Copyright (C) 2009 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 552 matching lines @@
     long m_vertexAttrib0BufferSize;
     GLfloat m_vertexAttrib0BufferValue[4];
     bool m_forceAttrib0BufferRefill;
     bool m_vertexAttrib0UsedBefore;
 
     PersistentWillBeMember<WebGLProgram> m_currentProgram;
     PersistentWillBeMember<WebGLFramebuffer> m_framebufferBinding;
     PersistentWillBeMember<WebGLRenderbuffer> m_renderbufferBinding;
     PersistentWillBeMember<CHROMIUMValuebuffer> m_valuebufferBinding;
 
-    GC_PLUGIN_IGNORE("crbug.com/496496")
     PersistentHeapVectorWillBeHeapVector<TextureUnitState> m_textureUnits;
     unsigned long m_activeTextureUnit;
 
     PersistentWillBeMember<WebGLTexture> m_blackTexture2D;
     PersistentWillBeMember<WebGLTexture> m_blackTextureCubeMap;
 
     Vector<GLenum> m_compressedTextureFormats;
 
     // Fixed-size cache of reusable image buffers for video texImage2D calls.
     class LRUImageBufferCache {
@@ skipping 520 matching lines @@
     static IntSize oldestContextSize();
 };
 
 DEFINE_TYPE_CASTS(WebGLRenderingContextBase, CanvasRenderingContext, context, context->is3d(), context.is3d());
 
 } // namespace blink
 
 WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(blink::WebGLRenderingContextBase::TextureUnitState);
 
 #endif // WebGLRenderingContextBase_h