Share Group plumbing in Blink; Remove WebGL from default share group

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index 547bcec99fac10d47461bac44de4998fc21ed832..763f8d8c47097124f8764f35003dc510ac7fc0c8 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -558,6 +558,7 @@ public:
     //
     // May return null if GPU is not supported.
     // Returns newly allocated and initialized offscreen WebGraphicsContext3D instance.
+    virtual WebGraphicsContext3D* createOffscreenGraphicsContext3D(const WebGraphicsContext3D::Attributes&, WebGraphicsContext3D* share_context) { return 0; }

[jamesr, 2014/03/17 21:01:22]

this is blink, so shareContext.

probably worth explaining what this parameter does in a brief comment

     virtual WebGraphicsContext3D* createOffscreenGraphicsContext3D(const WebGraphicsContext3D::Attributes&) { return 0; }
 
     // Returns a newly allocated and initialized offscreen context provider. The provider may return a null