OnDrawHardware() implementation with async messages

android_webview/browser/browser_view_renderer.cc

Index: android_webview/browser/browser_view_renderer.cc
diff --git a/android_webview/browser/browser_view_renderer.cc b/android_webview/browser/browser_view_renderer.cc
index 63e2f5cefaf497af9d25029a2336dd7a74e26aa2..b6fee63e8ccfe5e792bbda3c8e9d198f13a8fff0 100644
--- a/android_webview/browser/browser_view_renderer.cc
+++ b/android_webview/browser/browser_view_renderer.cc
@@ -9,6 +9,7 @@
 #include "android_webview/browser/browser_view_renderer_client.h"
 #include "android_webview/browser/child_frame.h"
 #include "android_webview/browser/compositor_frame_consumer.h"
+#include "android_webview/common/aw_switches.h"
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/logging.h"
@@ -106,7 +107,9 @@ BrowserViewRenderer::BrowserViewRenderer(
       max_page_scale_factor_(0.f),
       on_new_picture_enable_(false),
       clear_view_(false),
-      offscreen_pre_raster_(false) {}
+      offscreen_pre_raster_(false),
+      async_frame_messages_(base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kBVRAsyncFrameMessages)) {}
 
 BrowserViewRenderer::~BrowserViewRenderer() {
   DCHECK(compositor_map_.empty());
@@ -223,36 +226,49 @@ bool BrowserViewRenderer::OnDrawHardware() {
   ReturnResourceFromParent(current_compositor_frame_consumer_);
   UpdateMemoryPolicy();
 
-  gfx::Transform transform_for_tile_priority =
-      external_draw_constraints_.transform;
+  transform_for_tile_priority_ = external_draw_constraints_.transform;
 
   // If the WebView is on a layer, WebView does not know what transform is
   // applied onto the layer so global visible rect does not make sense here.
   // In this case, just use the surface rect for tiling.
-  gfx::Rect viewport_rect_for_tile_priority;
 
   // Leave viewport_rect_for_tile_priority empty if offscreen_pre_raster_ is on.
   if (!offscreen_pre_raster_ && !external_draw_constraints_.is_layer) {
-    viewport_rect_for_tile_priority = last_on_draw_global_visible_rect_;
+    viewport_rect_for_tile_priority_ = last_on_draw_global_visible_rect_;
   }
 
-  content::SynchronousCompositor::Frame frame = compositor_->DemandDrawHw(
-      size_, viewport_rect_for_tile_priority, transform_for_tile_priority);
-  if (!frame.frame.get()) {
-    TRACE_EVENT_INSTANT0("android_webview", "NoNewFrame",
-                         TRACE_EVENT_SCOPE_THREAD);
+  if (async_frame_messages_) {
+    compositor_->DemandDrawHwAsync(size_, viewport_rect_for_tile_priority_,
+                                   transform_for_tile_priority_);
     return current_compositor_frame_consumer_->HasFrameOnUI();
   }
 
+  frame_produced_ = false;

[boliu, 2016/08/23 02:39:52]

you don't need this, just check the frame before calling
OnDrawHardwareProcessFrame

[ojars, 2016/08/23 21:58:42]

Done.

+  content::SynchronousCompositor::Frame frame = compositor_->DemandDrawHw(
+      size_, viewport_rect_for_tile_priority_, transform_for_tile_priority_);
+  OnDrawHardwareProcessFrame(std::move(frame));
+
+  return (frame_produced_ ||
+          current_compositor_frame_consumer_->HasFrameOnUI());
+}
+
+void BrowserViewRenderer::OnDrawHardwareProcessFrame(
+    content::SynchronousCompositor::Frame frame) {
+  TRACE_EVENT0("android_webview",
+               "BrowserViewRenderer::OnDrawHardwareProcessFrame");
+  if (!frame.frame.get())
+    return;
+
+  frame_produced_ = true;
+
   std::unique_ptr<ChildFrame> child_frame = base::WrapUnique(new ChildFrame(
       frame.output_surface_id, std::move(frame.frame), compositor_id_,
-      viewport_rect_for_tile_priority.IsEmpty(), transform_for_tile_priority,
+      viewport_rect_for_tile_priority_.IsEmpty(), transform_for_tile_priority_,
       offscreen_pre_raster_, external_draw_constraints_.is_layer));
 
   ReturnUnusedResource(
       current_compositor_frame_consumer_->PassUncommittedFrameOnUI());
   current_compositor_frame_consumer_->SetFrameOnUI(std::move(child_frame));
-  return true;
 }
 
 void BrowserViewRenderer::OnParentDrawConstraintsUpdated(