Bug 857648 part 1. Remove unnecessary code that tries to filter out non-JS stack frames from a known-JS-only stack. r=khuey

dom/bindings/Exceptions.cpp

@@ -182,16 +182,7 @@ GetCurrentJSStack()
     return nullptr;
   }
 
-  // peel off native frames...
-  uint32_t language;
-  nsCOMPtr<nsIStackFrame> caller;
-  while (stack &&
-         NS_SUCCEEDED(stack->GetLanguage(&language)) &&
-         language != nsIProgrammingLanguage::JAVASCRIPT &&
-         NS_SUCCEEDED(stack->GetCaller(getter_AddRefs(caller))) &&
-         caller) {
-    stack = caller;
-  }
+  // Note that CreateStack only returns JS frames, so we're done here.
   return stack.forget();
 }