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..62d9e99020aa03c6a469b6c27f289041864d9c40 100644
--- a/android_webview/browser/browser_view_renderer.cc
+++ b/android_webview/browser/browser_view_renderer.cc
@@ -236,6 +236,15 @@ bool BrowserViewRenderer::OnDrawHardware() {
     viewport_rect_for_tile_priority = last_on_draw_global_visible_rect_;
   }
 
+  // If AFLAG true, will use semi-asynchronous implementation.
+  bool AFLAG = false;

[boliu, 2016/08/11 19:23:39]

Here is an example of an actual command line switch, although the CL is for
removing it

https://codereview.chromium.org/1913723002

basically you add a string to android_webview/common/aw_switches.cc/h, then
check for it using base::CommandLine::ForCurrentProcess

only check once though, not every frame

[ojars, 2016/08/17 22:51:33]

Done.

+  if (AFLAG) {
+    compositor_->DemandDrawHw_Async(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()) {
@@ -255,6 +264,37 @@ bool BrowserViewRenderer::OnDrawHardware() {
   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;
+
+  // 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_;
+  }
+
+  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,
+      offscreen_pre_raster_, external_draw_constraints_.is_layer));
+
+  ReturnUnusedResource(
+      current_compositor_frame_consumer_->PassUncommittedFrameOnUI());
+  current_compositor_frame_consumer_->SetFrameOnUI(std::move(child_frame));
+}
+
 void BrowserViewRenderer::OnParentDrawConstraintsUpdated(
     CompositorFrameConsumer* compositor_frame_consumer) {
   DCHECK(compositor_frame_consumer);