Bug 1254814 - Synthesize the key to inspect the element in the right process; r=testonly

In browser_markup_load_01.js, the browser context menu is opened and then the
Q key is pressed in order to choose the "inspect" menu item.
However this key is simulated in the content process, using the testActor.
Since the menu itself lives in the parent process, the key event should instead
be simulated in the parent process for it to work properly.

I suspect that this was sometimes causing the menu to stay open in subsequent
tests.

MozReview-Commit-ID: 1cOF7CSk7sm

--HG--
extra : rebase_source : d179968ff4521a291bf3f9ce7a6a71834bfa69bd
extra : histedit_source : 31957490cb17c5e873787578c09c9e628c267a7a

devtools/client/inspector/markup/test/browser_markup_load_01.js

@@ -58,7 +58,7 @@ function* chooseWithInspectElementContextMenu(selector, testActor) {
     button: 2
   }, gBrowser.selectedBrowser);
 
-  yield testActor.synthesizeKey({key: "Q", options: {}});
+  yield EventUtils.synthesizeKey("Q", {});
 }
 
 function waitForLinkedBrowserEvent(tab, event) {