Bug 1353060: Allow APZ in popup window widgets. r=kats

Prior to this patchset, we never hosted remote, scrollable content in widgets
other than toplevel and child windows, so all other widget types have APZ
disabled. Since we now need to host remote content in popup widgets, and would
like similar performance and behavior for those browsers as other remote
browsers, we also need to enable APZ for those widgets too.

MozReview-Commit-ID: AVDt9U5i2WK

widget/nsBaseWidget.cpp

@@ -923,7 +923,9 @@ bool
 nsBaseWidget::UseAPZ()
 {
   return (gfxPlatform::AsyncPanZoomEnabled() &&
-          (WindowType() == eWindowType_toplevel || WindowType() == eWindowType_child));
+          (WindowType() == eWindowType_toplevel ||
+           WindowType() == eWindowType_child ||
+           (WindowType() == eWindowType_popup && !IsSmallPopup())));
 }
 
 void nsBaseWidget::CreateCompositor()