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 26065be6d52e98b6a046ff9f49b735197c1f46c7..1fd64bafd168c5323849ce42f3b0302a063a82bf 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),
@@ -229,30 +232,57 @@ bool BrowserViewRenderer::OnDrawHardware() {
   // If the WebView is on a layer, WebView does not know what transform is

[boliu, 2016/08/29 22:02:10]

move this comment to the helper method

[ojars, 2016/09/02 01:29:55]

Done.

   // 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_;
+  gfx::Rect viewport_rect_for_tile_priority =
+      ComputeViewportRectForTilePriority();
+
+  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);
+

[boliu, 2016/08/29 22:02:10]

remove empty line

[ojars, 2016/09/02 01:29:55]

Done.

   if (!frame.frame.get()) {
     TRACE_EVENT_INSTANT0("android_webview", "NoNewFrame",
                          TRACE_EVENT_SCOPE_THREAD);
     return current_compositor_frame_consumer_->HasFrameOnUI();
   }
 
-  std::unique_ptr<ChildFrame> child_frame = base::MakeUnique<ChildFrame>(
+  OnDrawHardwareProcessFrame(std::move(frame));
+  return true;
+}
+
+void BrowserViewRenderer::OnDrawHardwareProcessFrame(
+    content::SynchronousCompositor::Frame frame) {
+  TRACE_EVENT0("android_webview",
+               "BrowserViewRenderer::OnDrawHardwareProcessFrame");
+  if (!frame.frame.get())

[dcheng, 2016/08/31 18:06:44]

Nit: I think .get() can probably be omitted here.

[ojars, 2016/09/02 01:29:55]

Done.

+    return;
+
+  gfx::Transform transform_for_tile_priority =
+      external_draw_constraints_.transform;
+  gfx::Rect viewport_rect_for_tile_priority =
+      ComputeViewportRectForTilePriority();
+  std::unique_ptr<ChildFrame> child_frame = base::WrapUnique(new ChildFrame(

[dcheng, 2016/08/31 18:06:44]

Nit: prefer base::MakeUnique<ChildFrame>();

[ojars, 2016/09/02 01:29:55]

Done.

[ojars, 2016/09/02 01:29:55]

Done.

       frame.output_surface_id, std::move(frame.frame), compositor_id_,
       viewport_rect_for_tile_priority.IsEmpty(), transform_for_tile_priority,
-      offscreen_pre_raster_, external_draw_constraints_.is_layer);
+      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;
+}
+
+gfx::Rect BrowserViewRenderer::ComputeViewportRectForTilePriority() {
+  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_;
+  }
+  return viewport_rect_for_tile_priority;
 }
 
 void BrowserViewRenderer::OnParentDrawConstraintsUpdated(