update getFramebufferAttachmentParameter for WebGL 2

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 0ef78d83b14a7bb41f96833fbe7df3a6f6976b8c..9137ffe8a87807ed2b7e23f2dde2413bb2b42564 100644
--- a/Source/core/html/canvas/WebGL2RenderingContextBase.h
+++ b/Source/core/html/canvas/WebGL2RenderingContextBase.h
@@ -164,12 +164,17 @@ public:
     void bindFramebuffer(GLenum target, 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;
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     WebGL2RenderingContextBase(HTMLCanvasElement*, PassOwnPtr<WebGraphicsContext3D>, const WebGLContextAttributes& requestedAttributes);
 
+    // Helper function to validate target and the attachment combination for getFramebufferAttachmentParameters.
+    // Generate GL error and return false if parameters are illegal.
+    bool validateGetFramebufferAttachmentParameterFunc(const char* functionName, GLenum target, GLenum attachment);
+
     bool validateClearBuffer(const char* functionName, GLenum buffer, GLsizei length);
 
     ScriptValue getInt64Parameter(ScriptState*, GLenum);