Use HitTestAggregator in GpuRootCompositorFrameSink

GpuRootCompositorFrameSink creates an instance of HitTestAggregator
and provides the notifications required when surfaces are added to the
next CompositorFrame, destroyed and when the next frame begins.

BUG=732399

Review-Url: https://codereview.chromium.org/2937233002
Cr-Commit-Position: refs/heads/master@{#487495}

components/viz/service/frame_sinks/gpu_root_compositor_frame_sink.cc

@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/command_line.h"
 #include "components/viz/service/display/display.h"
 #include "components/viz/service/frame_sinks/compositor_frame_sink_support.h"
 #include "components/viz/service/frame_sinks/frame_sink_manager.h"
@@ -118,7 +119,9 @@ void GpuRootCompositorFrameSink::DisplayOutputSurfaceLost() {
 
 void GpuRootCompositorFrameSink::DisplayWillDrawAndSwap(
     bool will_draw_and_swap,
-    const cc::RenderPassList& render_pass) {}
+    const cc::RenderPassList& render_pass) {
+  hit_test_aggregator_.PostTaskAggregate(display_->CurrentSurfaceId());
+}
 
 void GpuRootCompositorFrameSink::DisplayDidDrawAndSwap() {}
 
@@ -129,6 +132,7 @@ void GpuRootCompositorFrameSink::DidReceiveCompositorFrameAck(
 }
 
 void GpuRootCompositorFrameSink::OnBeginFrame(const cc::BeginFrameArgs& args) {
+  hit_test_aggregator_.Swap();
   if (client_)
     client_->OnBeginFrame(args);
 }

components/viz/service/frame_sinks/gpu_root_compositor_frame_sink.h

@@ -14,6 +14,7 @@
 #include "components/viz/service/display/display_client.h"
 #include "components/viz/service/frame_sinks/compositor_frame_sink_support_client.h"
 #include "components/viz/service/frame_sinks/gpu_compositor_frame_sink_delegate.h"
+#include "components/viz/service/hit_test/hit_test_aggregator.h"
 #include "mojo/public/cpp/bindings/associated_binding.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
@@ -101,6 +102,8 @@ class GpuRootCompositorFrameSink
       compositor_frame_sink_private_binding_;
   mojo::AssociatedBinding<cc::mojom::DisplayPrivate> display_private_binding_;
 
+  HitTestAggregator hit_test_aggregator_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuRootCompositorFrameSink);
 };
 

components/viz/service/hit_test/hit_test_aggregator.cc

@@ -133,7 +133,8 @@ void HitTestAggregator::Aggregate(const SurfaceId& display_surface_id) {
 
 void HitTestAggregator::AppendRoot(const SurfaceId& surface_id) {
   auto search = active_.find(surface_id);
-  DCHECK(search != active_.end());
+  if (search == active_.end())
+    return;
 
   mojom::HitTestRegionList* hit_test_region_list = search->second.get();