Force use of and cache render surface.

cc/surfaces/display.cc

Index: cc/surfaces/display.cc
diff --git a/cc/surfaces/display.cc b/cc/surfaces/display.cc
index 1f4c9d1abca99d3be4573db1707150fa41af6c19..dd9494b970d46cc2375b6079d59a73ea6ecf004b 100644
--- a/cc/surfaces/display.cc
+++ b/cc/surfaces/display.cc
@@ -277,8 +277,10 @@ bool Display::DrawAndSwap() {
                                      stored_latency_info_.end());
   stored_latency_info_.clear();
   bool have_copy_requests = false;
+  bool force_render_surface = false;
   for (const auto& pass : frame.render_pass_list) {
     have_copy_requests |= !pass->copy_requests.empty();
+    force_render_surface |= pass->force_render_surface;
   }
 
   gfx::Size surface_size;
@@ -299,7 +301,8 @@ bool Display::DrawAndSwap() {
   if (!size_matches)
     TRACE_EVENT_INSTANT0("cc", "Size mismatch.", TRACE_EVENT_SCOPE_THREAD);
 
-  bool should_draw = have_copy_requests || (have_damage && size_matches);
+  bool should_draw = force_render_surface || have_copy_requests ||

[reveman, 2017/05/10 13:06:17]

hm, I don't think this should force a draw. copy requests force a draw as that
basically a request to take a screenshot but there's still no need to redraw
unless something is damaged when using forced render surfaces.

[wutao, 2017/05/11 19:36:34]

Right.

+                     (have_damage && size_matches);
 
   // If the surface is suspended then the resources to be used by the draw are
   // likely destroyed.