cc: Remove EnsureRenderSurfaceLayerList, do UpdateDrawProps when needed.

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 45d533b5fb883c173067cdc4d549d793a819fb77..91f98aef8ff21df340b05ab07a209d788038bb9f 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -538,7 +538,7 @@ TEST_F(LayerTreeHostImplTest, ScrollWithoutRenderer) {
 
   // We should not crash when trying to scroll after the renderer initialization
   // fails.
-  EXPECT_EQ(InputHandler::ScrollIgnored,
+  EXPECT_EQ(InputHandler::ScrollStarted,

[enne (OOO), 2014/06/11 21:23:07]

Can you explain this change more?

[danakj, 2014/06/11 21:24:38]

While we're unable to UpdateDrawProperties, the ScrollBegin method can still
find the InnerViewportScrollLayer(), so it starts a scroll on that. That seems
equally okay as aborting the scroll to me, but I could add some extra early out
in ScrollBegin if you don't agree.

[enne (OOO), 2014/06/11 21:28:43]

Ah, ok.  That makes sense.  We no longer need a renderer to hit test.

[Ian Vollick, 2014/06/12 15:55:03]

Can you please add a 2nd check for a ScrollBegin at a point outside the
scrollers? It'd be nice if we had tests that checked that, even with an empty
RSLL (which was the old mode of failure, right?), we could still both scroll or
not scroll.

[danakj, 2014/06/12 16:03:58]

An empty RSLL only happens when there is no root layer or there is no renderer,
which this test and the one above do cover.

The ScrollMissesChild test covers scrolling outside all the layers.

[Ian Vollick, 2014/06/12 16:22:19]

What I was getting at was hit testing (for scrolling, etc) on layers that aren't
included in the RSLL, but that's unrelated to the test you're modifying here --
I don't think that this CL is reducing coverage, so ignore me :)

             host_impl_->ScrollBegin(gfx::Point(), InputHandler::Wheel));
 }