cc: Calculate "can use lcd text" on the compositor thread

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 4093c425eb19541fc3a05651e0318a13c1313eed..b3efd3d547451564865bbcc5c2a9377eaf8dce57 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -81,6 +81,7 @@ LayerTreeImpl::LayerTreeImpl(
     scoped_refptr<SyncedElasticOverscroll> elastic_overscroll)
     : layer_tree_host_impl_(layer_tree_host_impl),
       source_frame_number_(-1),
+      last_update_draw_properties_frame_number_(-1),
       hud_layer_(0),
       currently_scrolling_layer_(NULL),
       root_layer_scroll_offset_delegate_(NULL),
@@ -582,6 +583,25 @@ bool LayerTreeImpl::UpdateDrawProperties() {
     occlusion_tracker.set_minimum_tracking_size(
         settings().minimum_occlusion_tracking_size);
 
+    // It'd be ideal if this could be done earlier, but when the raster source

[danakj, 2015/02/18 01:25:52]

Can you move this out of the ::Occlusion {}? Maybe down with UpdateTiles?

[enne (OOO), 2015/02/18 19:43:05]

Done.

+    // is updated from the main thread during push properties, update draw
+    // properties has not occurred yet and so it's not clear whether or not the
+    // layer can or cannot use lcd text.  So, this is the cleanup pass to
+    // determine if the raster source needs to be replaced with a non-lcd
+    // raster source due to draw properties.
+    //
+    // TODO(enne): Make LTHI::sync_tree return this value.
+    LayerTreeImpl* sync_tree =
+        layer_tree_host_impl_->proxy()->CommitToActiveTree()
+            ? layer_tree_host_impl_->active_tree()
+            : layer_tree_host_impl_->pending_tree();
+    if (this == sync_tree &&
+        source_frame_number_ != last_update_draw_properties_frame_number_) {
+      for (const auto& layer : picture_layers_)
+        layer->UpdateCanUseLCDText();
+    }
+    last_update_draw_properties_frame_number_ = source_frame_number_;
+
     // LayerIterator is used here instead of CallFunctionForSubtree to only
     // UpdateTilePriorities on layers that will be visible (and thus have valid
     // draw properties) and not because any ordering is required.