Keeping track of descendants that draw content instead of recalcualting

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index a940e3487625981d71e6fe4e14bca2f2c7701249..c90cd393eb361cfbc82c2a1111746f9b63b711b0 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -1845,6 +1845,8 @@ TEST_F(LayerTreeHostImplTest, DidDrawCalledOnAllLayers) {
   EXPECT_FALSE(layer2->did_draw_called());
 
   LayerTreeHostImpl::FrameData frame;
+  FakeLayerTreeHostImpl::RecursiveUpdateNumChildren(
+      host_impl_->active_tree()->root_layer());
   EXPECT_EQ(DRAW_SUCCESS, host_impl_->PrepareToDraw(&frame));
   host_impl_->DrawLayers(&frame, gfx::FrameTime::Now());
   host_impl_->DidDrawAllLayers(frame);
@@ -3678,6 +3680,8 @@ TEST_F(LayerTreeHostImplTest, BlendingOffWhenDrawingOpaqueLayers) {
   layer1->SetUpdateRect(gfx::RectF(layer1->content_bounds()));
   layer2->SetExpectation(false, false);
   layer2->SetUpdateRect(gfx::RectF(layer1->content_bounds()));
+  FakeLayerTreeHostImpl::RecursiveUpdateNumChildren(
+      host_impl_->active_tree()->root_layer());
   EXPECT_EQ(DRAW_SUCCESS, host_impl_->PrepareToDraw(&frame));
   host_impl_->DrawLayers(&frame, gfx::FrameTime::Now());
   EXPECT_TRUE(layer1->quads_appended());