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

Source/core/html/canvas/WebGLRenderingContextBase.h

Index: Source/core/html/canvas/WebGLRenderingContextBase.h
diff --git a/Source/core/html/canvas/WebGLRenderingContextBase.h b/Source/core/html/canvas/WebGLRenderingContextBase.h
index 66f4187b4f059c5b02e20c26e7df8dbc047c269d..1195e519c30e3f20a0305d34c27d891de89fbd90 100644
--- a/Source/core/html/canvas/WebGLRenderingContextBase.h
+++ b/Source/core/html/canvas/WebGLRenderingContextBase.h
@@ -166,7 +166,7 @@ public:
     void cullFace(GLenum mode);
 
     void deleteBuffer(WebGLBuffer*);
-    void deleteFramebuffer(WebGLFramebuffer*);
+    virtual void deleteFramebuffer(WebGLFramebuffer*);
     void deleteProgram(WebGLProgram*);
     void deleteRenderbuffer(WebGLRenderbuffer*);
     void deleteShader(WebGLShader*);
@@ -780,7 +780,7 @@ protected:
     bool isTexInternalFormatColorBufferCombinationValid(GLenum texInternalFormat, GLenum colorBufferFormat);
 
     // Helper function to get the bound framebuffer's color buffer format.
-    GLenum boundFramebufferColorFormat();
+    virtual GLenum boundFramebufferColorFormat();
 
     // Helper function to verify limits on the length of uniform and attribute locations.
     bool validateLocationLength(const char* functionName, const String&);
@@ -895,6 +895,10 @@ protected:
     // Generate GL error if parameters are illegal.
     bool validateFramebufferFuncParameters(const char* functionName, GLenum target, GLenum attachment);
 
+    // Helper function to get draw Framebuffer target. Return GL_FRAMEBUFFER for
+    // WebGLRenderingContext. Return GL_DRAW_FRAMEBUFFER for WebGL2RenderingContext.
+    virtual GLenum getDrawFramebufferTarget();
+
     // Helper function to validate blend equation mode.
     bool validateBlendEquation(const char* functionName, GLenum);
 
@@ -990,7 +994,7 @@ protected:
     void setBackDrawBuffer(GLenum);
     void setFramebuffer(GLenum, WebGLFramebuffer*);
 
-    void restoreCurrentFramebuffer();
+    virtual void restoreCurrentFramebuffer();
     void restoreCurrentTexture2D();
 
     virtual void multisamplingChanged(bool) override;