Cache viewport rect for tile priority in UpdateTiles

cc/trees/layer_tree_impl_unittest.cc

Index: cc/trees/layer_tree_impl_unittest.cc
diff --git a/cc/trees/layer_tree_impl_unittest.cc b/cc/trees/layer_tree_impl_unittest.cc
index 2c5dd05be0372135e4c84b3acdd4d16f95993761..c50cb5cec8c20256b30c036b2defdda548c5d18a 100644
--- a/cc/trees/layer_tree_impl_unittest.cc
+++ b/cc/trees/layer_tree_impl_unittest.cc
@@ -2093,5 +2093,44 @@ TEST_F(LayerTreeImplTest, NumLayersSmallTree) {
   EXPECT_EQ(4u, host_impl().active_tree()->NumLayers());
 }
 
+TEST_F(LayerTreeImplTest, ViewportRectForTilePriorityIsCached) {
+  bool resourceless_software_draw = false;
+
+  gfx::Transform transform, transform_for_tile_priority;
+  gfx::Point3F transform_origin;
+  gfx::PointF position;
+  gfx::Size bounds(100, 100);
+  gfx::Rect viewport = gfx::Rect(0, 0, 200, 200),
+            rect1 = gfx::Rect(0, 0, 100, 100),
+            rect2 = gfx::Rect(10, 10, 123, 123);
+
+  scoped_ptr<LayerImpl> root = LayerImpl::Create(host_impl().active_tree(), 1);
+  SetLayerPropertiesForTesting(root.get(), transform, transform_origin,
+                               position, bounds, true, false, true);
+  root->SetDrawsContent(true);
+  host_impl().SetViewportSize(root->bounds());
+  host_impl().active_tree()->SetRootLayer(root.Pass());
+  host_impl().UpdateNumChildrenAndDrawPropertiesForActiveTree();
+
+  host_impl().SetExternalDrawConstraints(
+      transform, viewport, viewport,
+      rect1, /* viewport_rect_for_tile_priority */
+      transform_for_tile_priority, resourceless_software_draw);
+  host_impl().active_tree()->UpdateDrawProperties();
+  EXPECT_EQ(host_impl().active_tree()->ViewportRectForTilePriority(), rect1);
+
+  host_impl().SetExternalDrawConstraints(
+      transform, viewport, viewport,
+      rect2, /* viewport_rect_for_tile_priority */
+      transform_for_tile_priority, resourceless_software_draw);
+
+  // Test that even when the LTH's viewport rect for tile priority has
+  // changed, the ViewportRectForTilePriority will not change to most recent
+  // value until UpdateDrawProperties is called.
+  EXPECT_EQ(host_impl().active_tree()->ViewportRectForTilePriority(), rect1);
+  host_impl().active_tree()->UpdateDrawProperties();
+  EXPECT_EQ(host_impl().active_tree()->ViewportRectForTilePriority(), rect2);
+}
+
 }  // namespace
 }  // namespace cc