Force use of and cache render surface.

cc/output/direct_renderer.cc

 // Copyright 2012 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/output/direct_renderer.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 600 matching lines @@
   ScopedResource* texture = render_pass_textures_[render_pass->id].get();
   DCHECK(texture);
 
   gfx::Size size = RenderPassTextureSize(render_pass);
   size.Enlarge(enlarge_pass_texture_amount_.width(),
                enlarge_pass_texture_amount_.height());
   if (!texture->id()) {
     texture->Allocate(
         size, ResourceProvider::TEXTURE_HINT_IMMUTABLE_FRAMEBUFFER,
         BackbufferFormat(), current_frame()->current_render_pass->color_space);
+  } else {
+    if (render_pass->force_render_surface)

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

I'm not sure we can do this without also checking that render pass doesn't have
damage. We need to update the texture if it's damaged. If it's not damaged then
I think we can now return early here as it's not clipped when this flag is set.

We'll need comment here to explain this.

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

Tested in some animation and the render_pass->damage_rect get damaged for most
of time. Remove this early return for now. Improve late.

+      return false;
   }
   DCHECK(texture->id());
 
   if (BindFramebufferToTexture(texture)) {
     InitializeViewport(current_frame(), render_pass->output_rect,
                        gfx::Rect(render_pass->output_rect.size()),
                        texture->size());
     return true;
   }
 
   return false;
 }
 
 bool DirectRenderer::HasAllocatedResourcesForTesting(int render_pass_id) const {
   auto iter = render_pass_textures_.find(render_pass_id);
   return iter != render_pass_textures_.end() && iter->second->id();
 }
 
 // static
 gfx::Size DirectRenderer::RenderPassTextureSize(const RenderPass* render_pass) {
   return render_pass->output_rect.size();
 }
 
 void DirectRenderer::SetCurrentFrameForTesting(const DrawingFrame& frame) {
   current_frame_valid_ = true;
   current_frame_ = frame;
 }
 
 }  // namespace cc