Bug 1432637 - Schedule a composite when setting test properties on an APZC. r=botond

Scheduling a composition sets the mNeedsComposite flag in the compositor
scheduler, so that advancing the time via advanceTimeAndRefresh doesn't
do an early-exit.

MozReview-Commit-ID: KvldsCCY0SD

--HG--
extra : rebase_source : e661e430c36553ce95d7798b4bc95ffaab48ab90

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -4416,6 +4416,20 @@ void AsyncPanZoomController::ShareCompositorFrameMetrics()
   }
 }
 
+void
+AsyncPanZoomController::SetTestAsyncScrollOffset(const CSSPoint& aPoint)
+{
+  mTestAsyncScrollOffset = aPoint;
+  ScheduleComposite();
+}
+
+void
+AsyncPanZoomController::SetTestAsyncZoom(const LayerToParentLayerScale& aZoom)
+{
+  mTestAsyncZoom = aZoom;
+  ScheduleComposite();
+}
+
 Maybe<CSSPoint> AsyncPanZoomController::FindSnapPointNear(
     const CSSPoint& aDestination, nsIScrollableFrame::ScrollUnit aUnit) {
   mRecursiveMutex.AssertCurrentThreadIn();

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -1305,17 +1305,11 @@ public:
   /**
    * Set an extra offset for testing async scrolling.
    */
-  void SetTestAsyncScrollOffset(const CSSPoint& aPoint)
-  {
-    mTestAsyncScrollOffset = aPoint;
-  }
+  void SetTestAsyncScrollOffset(const CSSPoint& aPoint);
   /**
    * Set an extra offset for testing async scrolling.
    */
-  void SetTestAsyncZoom(const LayerToParentLayerScale& aZoom)
-  {
-    mTestAsyncZoom = aZoom;
-  }
+  void SetTestAsyncZoom(const LayerToParentLayerScale& aZoom);
 
   void MarkAsyncTransformAppliedToContent()
   {