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

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index f62a8664ff89f7e84467dc68813ae18ee56b99c0..5a90f057dace76ecedc44bc4be43100d02428883 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -565,6 +565,31 @@ void PictureLayerImpl::UpdateRasterSource(
       MaximumContentsScale());
 }
 
+void PictureLayerImpl::UpdateCanUseLCDText() {
+  // Don't allow the LCD text state to change once disabled.
+  if (!RasterSourceUsesLCDText())
+    return;
+  if (can_use_lcd_text() == RasterSourceUsesLCDText())
+    return;
+
+  // Raster sources are considered const, so in order to update the state
+  // a new one must be created and all tiles recreated.
+  scoped_refptr<RasterSource> new_raster_source =
+      raster_source_->CreateCloneWithoutLCDText();
+  // Synthetically invalidate everything.
+  gfx::Rect bounds_rect(bounds());
+  Region invalidation(bounds_rect);
+  UpdateRasterSource(new_raster_source, &invalidation, nullptr);

[danakj, 2015/02/18 01:24:10]

what if there is a pending tree, would this happen on both trees independently?
does that leave us not sharing tiles between the two trees, so they'll duplicate
raster work and slow down activation?

[enne (OOO), 2015/02/18 02:20:02]

This should only ever be called on the sync tree right after a commit, so is
equivalent to the PictureLayer::UpdateRasterSource call.  I can add DCHECKs here
to document those assumptions?

[danakj, 2015/02/18 02:28:13]

DCHECK is sync tree sounds good. 

+  SetUpdateRect(bounds_rect);
+
+  DCHECK(!RasterSourceUsesLCDText());
+}
+
+bool PictureLayerImpl::RasterSourceUsesLCDText() const {
+  return raster_source_ ? raster_source_->CanUseLCDText()
+                        : layer_tree_impl()->settings().can_use_lcd_text;
+}
+
 void PictureLayerImpl::NotifyTileStateChanged(const Tile* tile) {
   if (layer_tree_impl()->IsActiveTree()) {
     gfx::RectF layer_damage_rect =