Bug 1372405 - Change SchedulerGroup::GetName so it doesn't delegate to mozilla::Runnable (r=froydnj)

Delegating to mozilla::Runnable caused us to return the wrong value once
SchedulerGroup started passing a non-empty name to the Runnable constructor.

MozReview-Commit-ID: 2zMlpiMnHwv

xpcom/threads/SchedulerGroup.cpp

@@ -339,17 +339,15 @@ SchedulerGroup::Runnable::Runnable(already_AddRefed<nsIRunnable>&& aRunnable,
 NS_IMETHODIMP
 SchedulerGroup::Runnable::GetName(nsACString& aName)
 {
-  mozilla::Runnable::GetName(aName);
-  if (aName.IsEmpty()) {
-    // Try to get a name from the underlying runnable.
-    nsCOMPtr<nsINamed> named = do_QueryInterface(mRunnable);
-    if (named) {
-      named->GetName(aName);
-    }
-    if (aName.IsEmpty()) {
-      aName.AssignLiteral("anonymous");
-    }
+  // Try to get a name from the underlying runnable.
+  nsCOMPtr<nsINamed> named = do_QueryInterface(mRunnable);
+  if (named) {
+    named->GetName(aName);
   }
+  if (aName.IsEmpty()) {
+    aName.AssignLiteral("anonymous");
+  }
+
   aName.AppendASCII("(labeled)");
   return NS_OK;
 }