Remove cc::LayerTreeHostImpl::IsContextLost

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 2845d1897950097b67ee075b27d4daa630a24923..3922790c3f8c229b3b1cf87c4fcd8ef7b38ddd3f 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1102,6 +1102,9 @@ DrawResult LayerTreeHostImpl::PrepareToDraw(FrameData* frame) {
                "SourceFrameNumber",
                active_tree_->source_frame_number());
 
+  if (!have_valid_output_surface_)

[danakj, 2014/08/15 17:45:15]

For this to happen, we'd have to get the callback of a lost context in between
the Scheduler deciding to draw a frame and here. Is that possible? If it is, is
it worth having state/branches for when we could just draw to the lost context?

[dneto, 2014/08/15 17:58:20]

In a first attempt, I made LTHI::CanDraw return false when LTHI did not have a
valid output surface.  That caused mayhem in the layer-tree-host context-loss
unit tests, as it causes context loss in many of the points between starting
PrepareToDraw and DidDrawAllLayers, since many steps do DCHECK( CanDraw() ).

Is your suggestion similar?  I still am puzzled by when things can get
scheduled.

Or maybe I wasn't radical enough.  Could we always return true from
STP::DoComposite? And in that case we could also simplify
STP::CompositeImmediately a little.

[danakj, 2014/08/15 18:00:12]

Ya, make DoComposite return void. I'm suggesting that if the context is lost and
we're about to draw.. oh well draw anyways. The scheduler/embedder will hear
about it later and do something with it. Less branches keeps things simpler.

+    return DRAW_ABORTED_CONTEXT_LOST;
+
   if (need_to_update_visible_tiles_before_draw_ &&
       tile_manager_ && tile_manager_->UpdateVisibleTiles()) {
     DidInitializeVisibleTile();
@@ -1616,13 +1619,6 @@ void LayerTreeHostImpl::FinishAllRendering() {
     renderer_->Finish();
 }
 
-bool LayerTreeHostImpl::IsContextLost() {
-  DCHECK(proxy_->IsImplThread());
-  // To avoid races, rely only on the lost-surface callback.
-  // See crbug.com/392891.
-  return !have_valid_output_surface_;
-}
-
 void LayerTreeHostImpl::SetUseGpuRasterization(bool use_gpu) {
   if (use_gpu == use_gpu_rasterization_)
     return;
@@ -3297,7 +3293,7 @@ void LayerTreeHostImpl::CreateUIResource(UIResourceId uid,
     case UIResourceBitmap::ETC1:
       format = ETC1;
       break;
-  };
+  }

[dneto, 2014/08/15 17:44:31]

This fixes a readability issue reported when I first tried to upload the patch.

   id = resource_provider_->CreateResource(
       bitmap.GetSize(),
       wrap_mode,