Force use of and cache render surface.

cc/output/direct_renderer.cc

Index: cc/output/direct_renderer.cc
diff --git a/cc/output/direct_renderer.cc b/cc/output/direct_renderer.cc
index 5339f829c2b2b0af105efb910e636f5b47907b0c..213a14be838256eaeb6ae5b1a92cdad3c8270408 100644
--- a/cc/output/direct_renderer.cc
+++ b/cc/output/direct_renderer.cc
@@ -624,6 +624,12 @@ bool DirectRenderer::UseRenderPass(const RenderPass* render_pass) {
     texture->Allocate(
         size, ResourceProvider::TEXTURE_HINT_IMMUTABLE_FRAMEBUFFER,
         BackbufferFormat(), current_frame()->current_render_pass->color_space);
+  } else {
+    if (render_pass->force_render_surface &&

[jbauman, 2017/06/07 22:05:34]

Could we instead set the damage rectangle to empty in the surface aggregator,
and in the direct renderer avoid setting up the renderpass at all if the damage
rect is empty?

[wutao, 2017/06/09 02:31:32]

Sounds good and thanks for your sample cl.

The damage_rect also includes damage from the render surface itself. When
damage_rect is not empty, the render_pass may not have damage from contributing
render surfaces/layers/surface quads. Therefore, in both situations:
damage_rect.IsEmpty() or !(render_pass->has_damage_from_contributing_content()),
we can reuse the texture.

+        !(render_pass->has_property_change_on_contributing_render_surface ||
+          render_pass->has_damage_on_surface_quad)) {

[jbauman, 2017/05/30 22:04:07]

What exactly does it mean if there's damage on a surface quad here?
There shouldn't be any surface quads given to the direct renderer.

[wutao, 2017/05/30 23:12:52]

The surface_quad damage is accumulated during surface_aggregation and pass here
to indicate if we can reuse the texture. Since we do not have the concept of
surface quad (all should be flattened) in the renderer, we might give it
different name or grouped with other attribute/damage we will use at last.

+      return false;
+    }
   }
   DCHECK(texture->id());