cc: Introduce BeginFrame sequence numbers and acknowledgements.

content/browser/renderer_host/browser_compositor_view_mac.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/browser_compositor_view_mac.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 261 matching lines @@
   // Compute the frame size based on the root render pass rect size.
   cc::RenderPass* root_pass = frame.render_pass_list.back().get();
   float scale_factor = frame.metadata.device_scale_factor;
   gfx::Size pixel_size = root_pass->output_rect.size();
   gfx::Size dip_size = gfx::ConvertSizeToDIP(scale_factor, pixel_size);
   root_layer_->SetBounds(gfx::Rect(dip_size));
   if (recyclable_compositor_) {
     recyclable_compositor_->compositor()->SetScaleAndSize(scale_factor,
                                                           pixel_size);
   }
+  uint64_t begin_frame_source_id = frame.metadata.begin_frame_source_id;
+  uint64_t begin_frame_number = frame.metadata.begin_frame_number;
+  uint64_t oldest_incorporated_frame = frame.metadata.oldest_incorporated_frame;
+
   delegated_frame_host_->SwapDelegatedFrame(compositor_frame_sink_id,
                                             std::move(frame));
+
+  // The CompositorFrame's updates were only incorporated if it wasn't skipped.
+  bool has_updates = false;
+  if (!delegated_frame_host_->skipped_frames()) {
+    oldest_incorporated_frame_ = oldest_incorporated_frame;
+    has_updates = true;
+  }
+
+  cc::BeginFrameAck ack(begin_frame_source_id, begin_frame_number, has_updates,
+                        oldest_incorporated_frame_, 0);
+  if (begin_frame_source_)
+    begin_frame_source_->DidFinishFrame(this, ack);
+}
+
+void BrowserCompositorMac::OnBeginFrameDidNotDraw(cc::BeginFrameAck ack) {
+  // DelegatedFrameHost may have skipped the last frame(s).
+  ack.oldest_incorporated_frame = oldest_incorporated_frame_;
+  if (begin_frame_source_)
+    begin_frame_source_->DidFinishFrame(this, ack);
 }
 
 void BrowserCompositorMac::SetHasTransparentBackground(bool transparent) {
   has_transparent_background_ = transparent;
   if (recyclable_compositor_) {
     recyclable_compositor_->compositor()->SetHostHasTransparentBackground(
         has_transparent_background_);
   }
 }
 
@@ skipping 159 matching lines @@
 
 bool BrowserCompositorMac::IsAutoResizeEnabled() const {
   NOTREACHED();
   return false;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // cc::BeginFrameSourceBase, public:
 
 void BrowserCompositorMac::OnBeginFrame(const cc::BeginFrameArgs& args) {
+  if (args.source_id != last_begin_frame_args_.source_id) {
+    // Consider us up to date up to the previous BeginFrame.
+    oldest_incorporated_frame_ =
+        args.sequence_number > 0 ? args.sequence_number - 1 : 0;
+  }
+
   client_->BrowserCompositorMacSendBeginFrame(args);
   last_begin_frame_args_ = args;
 }
 
 const cc::BeginFrameArgs& BrowserCompositorMac::LastUsedBeginFrameArgs() const {
   return last_begin_frame_args_;
 }
 
 void BrowserCompositorMac::OnBeginFrameSourcePausedChanged(bool paused) {
   // Only used on Android WebView.
 }
 
 }  // namespace content