Optimize render passes with single quads

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 7554a97e3543219800d295c10faab1df75e5a728..99a75dc3de289534cbe9294dbc18fe5ccbe03549 100644
--- a/cc/output/direct_renderer.cc
+++ b/cc/output/direct_renderer.cc
@@ -141,14 +141,29 @@ DirectRenderer::DirectRenderer(RendererClient* client,
 
 DirectRenderer::~DirectRenderer() {}
 
+const TileDrawQuad* DirectRenderer::CanPassBeDrawnDirectly(
+    const RenderPass* pass) {
+  return nullptr;
+}
+
 void DirectRenderer::DecideRenderPassAllocationsForFrame(
     const RenderPassList& render_passes_in_draw_order) {
+  render_pass_bypass_quads_.clear();
+
   std::unordered_map<RenderPassId, gfx::Size, RenderPassIdHash>
       render_passes_in_frame;
-  for (size_t i = 0; i < render_passes_in_draw_order.size(); ++i)
+  RenderPass* root_render_pass = render_passes_in_draw_order.back().get();
+  for (size_t i = 0; i < render_passes_in_draw_order.size(); ++i) {
+    RenderPass* pass = render_passes_in_draw_order[i].get();
+    if (pass != root_render_pass) {

[enne (OOO), 2016/06/13 18:41:17]

Maybe we shouldn't drop the root render pass?

This fixes the context menu issue.

+      if (const TileDrawQuad* tile_quad = CanPassBeDrawnDirectly(pass)) {
+        render_pass_bypass_quads_[pass->id] = *tile_quad;
+        continue;
+      }
+    }
     render_passes_in_frame.insert(std::pair<RenderPassId, gfx::Size>(
-        render_passes_in_draw_order[i]->id,
-        RenderPassTextureSize(render_passes_in_draw_order[i].get())));
+        pass->id, RenderPassTextureSize(pass)));
+  }
 
   std::vector<RenderPassId> passes_to_delete;
   for (auto pass_iter = render_pass_textures_.begin();
@@ -405,6 +420,11 @@ void DirectRenderer::FlushPolygons(
 void DirectRenderer::DrawRenderPassAndExecuteCopyRequests(
     DrawingFrame* frame,
     RenderPass* render_pass) {
+  if (render_pass_bypass_quads_.find(render_pass->id) !=
+      render_pass_bypass_quads_.end()) {
+    return;
+  }
+
   DrawRenderPass(frame, render_pass);
 
   bool first_request = true;