Moved the majority of WebGL functionality into WebGLRenderingContextBase

Source/core/html/canvas/WebGLDepthTexture.h

Index: Source/core/html/canvas/WebGLDepthTexture.h
diff --git a/Source/core/html/canvas/WebGLDepthTexture.h b/Source/core/html/canvas/WebGLDepthTexture.h
index 75ee15f0d2be3ca254f6e26491f42ceaf4af7da8..15d51640e37f30b7b2c6c4a30e70d5a9b47a0b9c 100644
--- a/Source/core/html/canvas/WebGLDepthTexture.h
+++ b/Source/core/html/canvas/WebGLDepthTexture.h
@@ -34,15 +34,15 @@ namespace WebCore {
 
 class WebGLDepthTexture : public WebGLExtension, public ScriptWrappable {
 public:
-    static PassRefPtr<WebGLDepthTexture> create(WebGLRenderingContext*);
-    static bool supported(WebGLRenderingContext*);
+    static PassRefPtr<WebGLDepthTexture> create(WebGLRenderingContextBase*);
+    static bool supported(WebGLRenderingContextBase*);

[Zhenyao Mo, 2013/09/20 23:04:45]

I suggest we change supported(WebGLRenderingContextBase*) to
supported(GraphicsContext3D*), but it's not about whether this extension is
supported in a webgl context, but whether the underlying gl impl supports this. 
Using GraphicsContext3D will be semantically clear.

     static const char* getExtensionName();
 
     virtual ~WebGLDepthTexture();
     virtual ExtensionName getName() const;
 
 private:
-    WebGLDepthTexture(WebGLRenderingContext*);
+    WebGLDepthTexture(WebGLRenderingContextBase*);
 };
 
 } // namespace WebCore