Issue #2241 - Part 4.3: Move devtools over to getBounds().

This leaves getAdjustedQuads alone because it lives in its own world and its
result gets sent over IPC. That leaves things in a bit of an intermediate state,
but that should be OK for now.

Backported from Mozilla bug 1186265.

devtools/client/shared/test/browser_inplace-editor_autocomplete_offset.js

@@ -114,5 +114,5 @@ let runAutocompletionTest = Task.async(function* (editor) {
  */
 function getPopupOffset({popup, input}) {
   let popupQuads = popup._panel.getBoxQuads({relativeTo: input});
-  return popupQuads[0].bounds.left;
+  return popupQuads[0].getBounds().left;
 }