Fix ExternalViewportRectForPrioritizingTiles flakiness on Windows

2 problems here:
1. Setting the frame time to 0 does nothing, because LTHI will read from
gfx::FrameTime::Now() instead. Need to start at 1 millisecond.

2. Need to tick the frame timer after SetupDrawPropertiesAndUpdateTiles.

BUG=399796

Review URL: https://codereview.chromium.org/444463004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287536 0039d316-1c4b-4281-b951-d872f2087c98

cc/layers/picture_layer_impl_unittest.cc

@@ -303,9 +303,9 @@ TEST_F(PictureLayerImplTest, CloneNoInvalidation) {
     VerifyAllTilesExistAndHavePile(tilings->tiling_at(i), active_pile.get());
 }
 
-TEST_F(PictureLayerImplTest,
-       DISABLED_ExternalViewportRectForPrioritizingTiles) {
+TEST_F(PictureLayerImplTest, ExternalViewportRectForPrioritizingTiles) {
   base::TimeTicks time_ticks;
+  time_ticks += base::TimeDelta::FromMilliseconds(1);
   host_impl_.SetCurrentFrameTimeTicks(time_ticks);
   gfx::Size tile_size(100, 100);
   gfx::Size layer_bounds(400, 400);
@@ -321,6 +321,9 @@ TEST_F(PictureLayerImplTest,
   AddDefaultTilingsWithInvalidation(invalidation);
   SetupDrawPropertiesAndUpdateTiles(active_layer_, 1.f, 1.f, 1.f, 1.f, false);
 
+  time_ticks += base::TimeDelta::FromMilliseconds(200);
+  host_impl_.SetCurrentFrameTimeTicks(time_ticks);
+
   // Update tiles with viewport for tile priority as (0, 0, 100, 100) and the
   // identify transform for tile priority.
   bool resourceless_software_draw = false;