Fix software compositor responsiveness

Force new frames to be drawn before acknowledging them. This
ensures that the renderer will not produce another frame before
the old frame has finished drawing. For fast animations on high
resolution displays, the new frame can immediately demand to be
drawn right after the old frame, giving no time to process input
events.

This was done by the (now defunct) legacy software path in
DidUpdateBackingStore. This updates software compositor to do
the same.

BUG=347274

Review URL: https://codereview.chromium.org/182203002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253738 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 17 insertions, 4 deletions

diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 0107a67..66e4c3c 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -1804,18 +1804,31 @@ void RenderWidgetHostViewMac::OnSwapCompositorFrame(
     return;
   }
 
+  // Add latency info to report when the frame finishes drawing.
+  AddPendingLatencyInfo(frame->metadata.latency_info);
+  GotSoftwareFrame();
+
+  // Draw the contents of the frame immediately. It is critical that this
+  // happen before the frame be acked, otherwise the new frame will likely be
+  // ready before the drawing is complete, thrashing the browser main thread.
+  if (use_core_animation_) {
+    [software_layer_ setNeedsDisplay];
+    if (!about_to_validate_and_paint_)
+      [software_layer_ displayIfNeeded];
+  } else {
+    [cocoa_view_ setNeedsDisplay:YES];
+    if (!about_to_validate_and_paint_)
+      [cocoa_view_ displayIfNeeded];
+  }
+
   cc::CompositorFrameAck ack;
   RenderWidgetHostImpl::SendSwapCompositorFrameAck(
       render_widget_host_->GetRoutingID(),
       software_frame_manager_->GetCurrentFrameOutputSurfaceId(),
       render_widget_host_->GetProcess()->GetID(),
       ack);
-  AddPendingLatencyInfo(frame->metadata.latency_info);
   software_frame_manager_->SwapToNewFrameComplete(
       !render_widget_host_->is_hidden());
-
-  GotSoftwareFrame();
-  [cocoa_view_ setNeedsDisplay:YES];
 }
 
 void RenderWidgetHostViewMac::OnAcceleratedCompositingStateChange() {