Add a hide_layer_and_subtree() flag to cc::Layer

cc/trees/layer_tree_host_common.cc

Index: cc/trees/layer_tree_host_common.cc
diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index 2e3d8402c7e9b078b10c796afc2854732626df35..4a616eb942bc450f875cabda5b1cde8db7a21d1f 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -232,6 +232,10 @@ static bool LayerShouldBeSkipped(LayerType* layer) {
 }
 
 static inline bool SubtreeShouldBeSkipped(LayerImpl* layer) {
+  // The embedder can request to hide the entire layer's subtree.
+  if (layer->hide_layer_and_subtree())
+    return true;
+
   // If layer is on the pending tree and opacity is being animated then
   // this subtree can't be skipped as we need to create, prioritize and
   // include tiles for this layer when deciding if tree can be activated.
@@ -245,6 +249,10 @@ static inline bool SubtreeShouldBeSkipped(LayerImpl* layer) {
 }
 
 static inline bool SubtreeShouldBeSkipped(Layer* layer) {
+  // The embedder can request to hide the entire layer's subtree.
+  if (layer->hide_layer_and_subtree())
+    return true;
+
   // If the opacity is being animated then the opacity on the main thread is
   // unreliable (since the impl thread may be using a different opacity), so it
   // should not be trusted.
@@ -1493,7 +1501,7 @@ static void CalculateDrawPropertiesInternal(
   UpdateTilePrioritiesForLayer(layer);
 
   // If neither this layer nor any of its children were added, early out.
-  if (sorting_start_index == descendants.size())
+  if (!IsRootLayer(layer) && sorting_start_index == descendants.size())

[enne (OOO), 2013/06/20 00:17:47]

If the root layer doesn't draw, why does it need to save paint properties?

[danakj, 2013/06/20 00:20:04]

Because otherwise the impl layer doesn't get the real values pushed. Right now
that's just bounds, so the impl root layer always has bounds 0x0 even though we
have a bounds on the main thread. That seems wrong, though not hugely
problematic in practice.

     return;
 
   // If preserves-3d then sort all the descendants in 3D so that they can be