cc: HUD handle context lost in Gpu raster.

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 67f5b43ffdcf902a5bc7130b96263076854c8dfc..5faf88a3b05ff5e0c3490c1295856b3359b92d5b 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1701,13 +1701,16 @@ bool LayerTreeHostImpl::DrawLayers(FrameData* frame) {
   }
 
   const DrawMode draw_mode = GetDrawMode();
+  uint32_t evict_res_id = 0U;

[vmpstr, 2017/06/30 23:16:51]

ResourceId? also evict_resource_id.

[sohan, 2017/07/04 16:51:13]

Done.

 
   // Because the contents of the HUD depend on everything else in the frame, the
   // contents of its texture are updated as the last thing before the frame is
   // drawn.
   if (active_tree_->hud_layer()) {
     TRACE_EVENT0("cc", "DrawLayers.UpdateHudTexture");
-    active_tree_->hud_layer()->UpdateHudTexture(
+    // For Ganesh backed HUD, a context loss may cause the drawing canvas to be
+    // invalid, return the resource id to evicted from quadlist.
+    evict_res_id = active_tree_->hud_layer()->UpdateHudTexture(
         draw_mode, resource_provider_.get(),
         layer_tree_frame_sink_->context_provider());
   }
@@ -1734,8 +1737,11 @@ bool LayerTreeHostImpl::DrawLayers(FrameData* frame) {
   ResourceProvider::ResourceIdArray resources;
   for (const auto& render_pass : frame->render_passes) {
     for (auto* quad : render_pass->quad_list) {
-      for (ResourceId resource_id : quad->resources)
-        resources.push_back(resource_id);
+      for (ResourceId resource_id : quad->resources) {
+        if (resource_id != evict_res_id) {

[vmpstr, 2017/06/30 23:16:51]

This doesn't look right. 

The resource should not be in the quad list if it's evicted. Maybe check this
during HUDLayerImpl::AppendQuads instead and keep all of the logic limited to
that class?

[sohan, 2017/07/04 16:51:13]

Yeah this is kinda odd.
The problem is for HUD layers, append quad happens before sksurface creation (in
UpdateHudTexture for ganesh backend) and if the context loss happens during
surface creation, we are stuck with the resource in quad list.
We can of course traverse the renderpass and evict, but thought it is more
efficient to avoid passing to resource array here. wdyt ?

+          resources.push_back(resource_id);
+        }
+      }
     }
   }