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..ce8e01135ff4be9bbf5526a26d7c32393aa16478 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"
@@ -93,6 +94,8 @@ BrowserViewRenderer::BrowserViewRenderer(
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner)
     : client_(client),
       ui_task_runner_(ui_task_runner),
+      async_on_draw_hardware_(base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kAsyncOnDrawHardware)),
       current_compositor_frame_consumer_(nullptr),
       compositor_(nullptr),
       is_paused_(false),
@@ -236,12 +239,35 @@ bool BrowserViewRenderer::OnDrawHardware() {
     viewport_rect_for_tile_priority = last_on_draw_global_visible_rect_;
   }
 
+  if (async_on_draw_hardware_) {
+    compositor_->DemandDrawHwAsync(size_, viewport_rect_for_tile_priority,
+                                   transform_for_tile_priority);
+    return current_compositor_frame_consumer_->HasFrameOnUI();
+  }
+
   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 (!frame.frame.get())
     return current_compositor_frame_consumer_->HasFrameOnUI();

[boliu, 2016/08/23 22:08:01]

there used to be an TRACE_EVENT_INSTANT0 here, don't drop it

[ojars, 2016/08/29 21:54:45]

Done.

+
+  OnDrawHardwareProcessFrame(std::move(frame));
+  return true;
+}
+
+void BrowserViewRenderer::OnDrawHardwareProcessFrame(
+    content::SynchronousCompositor::Frame frame) {
+  TRACE_EVENT0("android_webview",
+               "BrowserViewRenderer::OnDrawHardwareProcessFrame");
+  if (!frame.frame.get())
+    return;
+
+  gfx::Transform transform_for_tile_priority =
+      external_draw_constraints_.transform;
+  gfx::Rect viewport_rect_for_tile_priority;
+
+  if (!offscreen_pre_raster_ && !external_draw_constraints_.is_layer) {
+    viewport_rect_for_tile_priority = last_on_draw_global_visible_rect_;

[boliu, 2016/08/23 22:08:01]

factor this duplicate code into a helper method, like
ComputeViewportRectForTilePriority

[ojars, 2016/08/29 21:54:45]

Done.

   }
 
   std::unique_ptr<ChildFrame> child_frame = base::WrapUnique(new ChildFrame(
@@ -252,7 +278,6 @@ bool BrowserViewRenderer::OnDrawHardware() {
   ReturnUnusedResource(
       current_compositor_frame_consumer_->PassUncommittedFrameOnUI());
   current_compositor_frame_consumer_->SetFrameOnUI(std::move(child_frame));
-  return true;
 }
 
 void BrowserViewRenderer::OnParentDrawConstraintsUpdated(