WebGL 2: add read/write framebuffer binding points to related APIs

Source/core/html/canvas/WebGL2RenderingContextBase.h

Index: Source/core/html/canvas/WebGL2RenderingContextBase.h
diff --git a/Source/core/html/canvas/WebGL2RenderingContextBase.h b/Source/core/html/canvas/WebGL2RenderingContextBase.h
index 27495734972c5494462a4285b1b3570a15d19b46..e65567874f845f205c50c51b7cf588f6f995c46e 100644
--- a/Source/core/html/canvas/WebGL2RenderingContextBase.h
+++ b/Source/core/html/canvas/WebGL2RenderingContextBase.h
@@ -162,9 +162,11 @@ public:
     /* WebGLRenderingContextBase overrides */
     void initializeNewContext() override;
     void bindFramebuffer(GLenum target, WebGLFramebuffer*) override;
+    void deleteFramebuffer(WebGLFramebuffer*) override;
     ScriptValue getParameter(ScriptState*, GLenum pname) override;
     ScriptValue getTexParameter(ScriptState*, GLenum target, GLenum pname) override;
     ScriptValue getFramebufferAttachmentParameter(ScriptState*, GLenum target, GLenum attachment, GLenum pname) override;
+    void restoreCurrentFramebuffer() override;
 
     DECLARE_VIRTUAL_TRACE();
 
@@ -196,6 +198,8 @@ protected:
     bool validateFramebufferTarget(GLenum target) override;
     WebGLFramebuffer* getFramebufferBinding(GLenum target) override;
     GLint getMaxTextureLevelForTarget(GLenum target) override;
+    GLenum boundFramebufferColorFormat() override;
+    GLenum getDrawFramebufferTarget() override;
 
     RefPtrWillBeMember<WebGLFramebuffer> m_readFramebufferBinding;
     GLint m_max3DTextureSize;