Force use of and cache render surface.

cc/surfaces/display.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/surfaces/display.h"
 
 #include <stddef.h>
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 259 matching lines @@
     Surface* surface = surface_manager_->GetSurfaceForId(id_entry.first);
     if (surface)
       surface->RunDrawCallback();
   }
 
   frame.metadata.latency_info.insert(frame.metadata.latency_info.end(),
                                      stored_latency_info_.begin(),
                                      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;
   bool have_damage = false;
   RenderPass& last_render_pass = *frame.render_pass_list.back();
   if (last_render_pass.output_rect.size() != current_surface_size_ &&
       last_render_pass.damage_rect == last_render_pass.output_rect &&
       !current_surface_size_.IsEmpty()) {
     // Resize the output rect to the current surface size so that we won't
     // skip the draw and so that the GL swap won't stretch the output.
     last_render_pass.output_rect.set_size(current_surface_size_);
     last_render_pass.damage_rect = last_render_pass.output_rect;
   }
   surface_size = last_render_pass.output_rect.size();
   have_damage = !last_render_pass.damage_rect.size().IsEmpty();
 
   bool size_matches = surface_size == current_surface_size_;
   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.
   if (output_surface_->SurfaceIsSuspendForRecycle()) {
     TRACE_EVENT_INSTANT0("cc", "Surface is suspended for recycle.",
                          TRACE_EVENT_SCOPE_THREAD);
     should_draw = false;
   }
 
   client_->DisplayWillDrawAndSwap(should_draw, frame.render_pass_list);
@@ skipping 102 matching lines @@
 const SurfaceId& Display::CurrentSurfaceId() {
   return current_surface_id_;
 }
 
 void Display::ForceImmediateDrawAndSwapIfPossible() {
   if (scheduler_)
     scheduler_->ForceImmediateSwapIfPossible();
 }
 
 }  // namespace cc