Bug 1719855 - Fix DoLongPressPreventDefaultTest to scroll down the co…

…ntent by touch events. r=botond

Originally the test tried to scroll up, thus the content didn't scroll at all.

Now with scrolling down touch events, the content scrolls down even if the
long-tap event was preventDefaulted.

Depends on D176480

Differential Revision: https://phabricator.services.mozilla.com/D176481

gfx/layers/apz/test/gtest/TestGestureDetector.cpp

@@ -487,7 +487,7 @@ class APZCLongPressTester : public APZCGestureDetectorTester {
     // an APZC even if the long-tap event was preventDefaulted.
     EXPECT_CALL(*mcc, RequestContentRepaint(_)).Times(1);
 
-    int touchX = 10, touchStartY = 10, touchEndY = 50;
+    int touchX = 10, touchStartY = 50, touchEndY = 10;
 
     APZEventResult result =
         TouchDown(apzc, ScreenIntPoint(touchX, touchStartY), mcc->Time());
@@ -547,8 +547,8 @@ class APZCLongPressTester : public APZCGestureDetectorTester {
     AsyncTransform viewTransformOut;
     apzc->SampleContentTransformForFrame(&viewTransformOut, pointOut);
 
-    EXPECT_EQ(ParentLayerPoint(), pointOut);
-    EXPECT_EQ(AsyncTransform(), viewTransformOut);
+    EXPECT_GT(pointOut.y, 0);
+    EXPECT_LT(viewTransformOut.mTranslation.y, 0);
 
     apzc->AssertStateIsReset();
   }