Fix ExternalViewportRectForPrioritizingTiles flakiness on windows

cc/layers/picture_layer_impl_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <utility>
@@ skipping 285 matching lines @@
 
   EXPECT_EQ(pending_layer_->tilings()->num_tilings(),
             active_layer_->tilings()->num_tilings());
 
   const PictureLayerTilingSet* tilings = pending_layer_->tilings();
   EXPECT_GT(tilings->num_tilings(), 0u);
   for (size_t i = 0; i < tilings->num_tilings(); ++i)
     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);
 
   scoped_refptr<FakePicturePileImpl> pending_pile =
       FakePicturePileImpl::CreateFilledPile(tile_size, layer_bounds);
   scoped_refptr<FakePicturePileImpl> active_pile =
       FakePicturePileImpl::CreateFilledPile(tile_size, layer_bounds);
 
   SetupTrees(pending_pile, active_pile);
 
   Region invalidation;
   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;
   gfx::Rect viewport = gfx::Rect(layer_bounds),
             viewport_rect_for_tile_priority = gfx::Rect(0, 0, 100, 100);
   gfx::Transform transform, transform_for_tile_priority;
 
   host_impl_.SetExternalDrawConstraints(transform,
                                         viewport,
                                         viewport,
@@ skipping 3368 matching lines @@
 
   host_impl_.tile_manager()->InitializeTilesWithResourcesForTesting(all_tiles);
 
   VerifyEvictionConsidersOcclusion(pending_layer_,
                                    total_expected_occluded_tile_count);
   VerifyEvictionConsidersOcclusion(active_layer_,
                                    total_expected_occluded_tile_count);
 }
 }  // namespace
 }  // namespace cc