--- a/content/canvas/src/WebGLContextGL.cpp
+++ b/content/canvas/src/WebGLContextGL.cpp
@@ -4196,8 +4196,15 @@ int mozilla::GetWebGLTexelFormat(GLenum 
             case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
                 return WebGLTexelFormat::RGB565;
             default:
                 NS_ASSERTION(PR_FALSE, "Coding mistake?! Should never reach this point.");
                 return WebGLTexelFormat::Generic;
         }
     }
 }
+
+NS_IMETHODIMP
+WebGLContext::GetExtension(const nsAString& aName, nsISupports **retval)
+{
+    *retval = nsnull;
+    return NS_OK;
+}

--- a/dom/interfaces/canvas/nsIDOMWebGLRenderingContext.idl
+++ b/dom/interfaces/canvas/nsIDOMWebGLRenderingContext.idl
@@ -829,9 +829,12 @@ interface nsIDOMWebGLRenderingContext : 
   void vertexAttribPointer(in WebGLuint idx, in WebGLint size, in WebGLenum type, in WebGLboolean normalized, in WebGLsizei stride, in WebGLsizeiptr offset);
 
   void viewport(in WebGLint x, in WebGLint y, in WebGLsizei width, in WebGLsizei height);
 
   // get an underlying GL parameter, without any WebGL intervention.
   // Most useful for querying GL_VENDOR/GL_RENDERER for identifying
   // the underlying renderer to the user.
   [noscript] DOMString mozGetUnderlyingParamString(in WebGLenum pname);
+
+  // extensions
+  nsISupports getExtension(in DOMString name);
 };