[cc] Pass on BeginFrameAcks from CompositorEBFS through RWHVAura, DFH.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 1000c12f3f4f68d67ca1f1d5ad571e50f92963a4..3a06ae7fd5ffb637a7e0afd0e5fe539e16171973 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -387,6 +387,8 @@ RenderWidgetHostViewAura::RenderWidgetHostViewAura(RenderWidgetHost* host,
       is_loading_(false),
       has_composition_text_(false),
       begin_frame_source_(nullptr),
+      latest_confirmed_begin_frame_sequence_number_(
+          cc::BeginFrameArgs::kInvalidFrameNumber),
       needs_begin_frames_(false),
       needs_flush_input_(false),
       added_frame_observer_(false),
@@ -675,8 +677,13 @@ void RenderWidgetHostViewAura::UpdateNeedsBeginFramesInternal() {
     begin_frame_source_->RemoveObserver(this);
 }
 
-void RenderWidgetHostViewAura::OnBeginFrame(
-    const cc::BeginFrameArgs& args) {
+void RenderWidgetHostViewAura::OnBeginFrame(const cc::BeginFrameArgs& args) {
+  if (args.source_id != last_begin_frame_args_.source_id) {
+    // Source changed, we don't know our freshness anymore.
+    latest_confirmed_begin_frame_sequence_number_ =
+        cc::BeginFrameArgs::kInvalidFrameNumber;
+  }
+
   needs_flush_input_ = false;
   host_->FlushInput();
   UpdateNeedsBeginFramesInternal();
@@ -950,6 +957,37 @@ void RenderWidgetHostViewAura::OnSwapCompositorFrame(
   }
   selection_controller_->OnSelectionBoundsChanged(selection.start,
                                                   selection.end);
+
+  cc::BeginFrameAck ack(frame.metadata.begin_frame_ack);
+  DCHECK_LE(cc::BeginFrameArgs::kStartingFrameNumber, ack.sequence_number);
+  // The CompositorFrame's damage was only incorporated if it wasn't skipped.
+  if (delegated_frame_host_->skipped_frames()) {

[piman, 2017/03/14 20:06:44]

delegated_frame_host_ may not exist (e.g. if IsMus() is true, we don't create it
- see other checks in this file).

[Eric Seckler, 2017/03/15 11:56:48]

Code moved, checks aren't necessary anymore.

+    ack.has_damage = false;
+    ack.latest_confirmed_sequence_number =
+        latest_confirmed_begin_frame_sequence_number_;
+  } else {
+    DCHECK(ack.has_damage);
+    latest_confirmed_begin_frame_sequence_number_ =
+        ack.latest_confirmed_sequence_number;
+  }

[piman, 2017/03/14 20:06:44]

Could it be useful to move this logic to DelegatedFrameHost, so that it also
applies to Mac?

[Eric Seckler, 2017/03/15 11:56:48]

Sounds good, done. I'll add the actual calls to DidFinishFrame in RWHVMac in a
separate patch.

+
+  if (begin_frame_source_)
+    begin_frame_source_->DidFinishFrame(this, ack);
+}
+
+void RenderWidgetHostViewAura::OnBeginFrameDidNotSwap(
+    const cc::BeginFrameAck& ack) {
+  DCHECK_LE(cc::BeginFrameArgs::kStartingFrameNumber, ack.sequence_number);
+  DCHECK(!ack.has_damage);
+  cc::BeginFrameAck modified_ack = ack;
+  if (delegated_frame_host_->skipped_frames()) {

[piman, 2017/03/14 20:06:44]

ditto, delegated_frame_host_ may not exist

[Eric Seckler, 2017/03/15 11:56:48]

Gone, too.

+    // If DelegatedFrameHost skipped the last frame(s), we need to wait for a
+    // newly submitted CompositorFrame before confirming newer sequence numbers.
+    modified_ack.latest_confirmed_sequence_number =
+        latest_confirmed_begin_frame_sequence_number_;
+  }
+  if (begin_frame_source_)
+    begin_frame_source_->DidFinishFrame(this, modified_ack);
 }
 
 void RenderWidgetHostViewAura::ClearCompositorFrame() {