Provide simple fling bookkeeping for telemetry

Have the InputRouter track active renderer flings, rather than all
flings as was tried in the original change that was reverted in
crrev.com/1113143002. Also re-enable the
smoothness.fling.simple_mobile_sites telemetry benchmark, and
ensure WebView DidStopFlinging notifications are consistent with
other platforms.

BUG=483037

Review URL: https://codereview.chromium.org/1125713004

Cr-Commit-Position: refs/heads/master@{#328801}

5 files changed, 69 insertions, 8 deletions

diff --git a/content/browser/android/in_process/synchronous_compositor_impl.cc b/content/browser/android/in_process/synchronous_compositor_impl.cc
index 823a897..24232ae 100644
--- a/content/browser/android/in_process/synchronous_compositor_impl.cc
+++ b/content/browser/android/in_process/synchronous_compositor_impl.cc
@@ -15,6 +15,7 @@
 #include "content/browser/android/in_process/synchronous_input_event_filter.h"
 #include "content/browser/renderer_host/render_widget_host_view_android.h"
 #include "content/common/input/did_overscroll_params.h"
+#include "content/common/input_messages.h"
 #include "content/public/browser/android/synchronous_compositor_client.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
@@ -287,10 +288,11 @@ void SynchronousCompositorImpl::DidOverscroll(
 }
 
 void SynchronousCompositorImpl::DidStopFlinging() {
-  RenderWidgetHostViewAndroid* rwhv = static_cast<RenderWidgetHostViewAndroid*>(
-      contents_->GetRenderWidgetHostView());
-  if (rwhv)
-    rwhv->DidStopFlinging();
+  // It's important that the fling-end notification follow the same path as it
+  // takes on other platforms (using an IPC). This ensures consistent
+  // bookkeeping at all stages of the input pipeline.
+  contents_->GetRenderProcessHost()->OnMessageReceived(
+      InputHostMsg_DidStopFlinging(routing_id_));
 }
 
 InputEventAckState SynchronousCompositorImpl::HandleInputEvent(
diff --git a/content/browser/renderer_host/input/input_router_impl.cc b/content/browser/renderer_host/input/input_router_impl.cc
index df02bb4..ed0ebb0 100644
--- a/content/browser/renderer_host/input/input_router_impl.cc
+++ b/content/browser/renderer_host/input/input_router_impl.cc
@@ -76,6 +76,7 @@ InputRouterImpl::InputRouterImpl(IPC::Sender* sender,
       current_view_flags_(0),
       current_ack_source_(ACK_SOURCE_NONE),
       flush_requested_(false),
+      active_renderer_fling_count_(0),
       touch_event_queue_(this, config.touch_config),
       gesture_event_queue_(this, this, config.gesture_config) {
   DCHECK(sender);
@@ -251,7 +252,8 @@ bool InputRouterImpl::HasPendingEvents() const {
          mouse_move_pending_ ||
          mouse_wheel_pending_ ||
          select_message_pending_ ||
-         move_caret_pending_;
+         move_caret_pending_ ||
+         active_renderer_fling_count_ > 0;
 }
 
 bool InputRouterImpl::OnMessageReceived(const IPC::Message& message) {
@@ -497,8 +499,13 @@ void InputRouterImpl::OnSetTouchAction(TouchAction touch_action) {
 }
 
 void InputRouterImpl::OnDidStopFlinging() {
-  // TODO(jdduke): Track fling status to allow flush notifications after a fling
-  // has terminated, crbug.com/483037.
+  DCHECK_GT(active_renderer_fling_count_, 0);
+  // Note that we're only guaranteed to get a fling end notification from the
+  // renderer, not from any other consumers. Consequently, the GestureEventQueue
+  // cannot use this bookkeeping for logic like tap suppression.
+  --active_renderer_fling_count_;
+  SignalFlushedIfNecessary();
+
   client_->DidStopFlinging();
 }
 
@@ -603,6 +610,12 @@ void InputRouterImpl::ProcessWheelAck(InputEventAckState ack_result,
 void InputRouterImpl::ProcessGestureAck(WebInputEvent::Type type,
                                         InputEventAckState ack_result,
                                         const ui::LatencyInfo& latency) {
+  if (type == blink::WebInputEvent::GestureFlingStart &&
+      ack_result == INPUT_EVENT_ACK_STATE_CONSUMED &&
+      current_ack_source_ == RENDERER) {
+    ++active_renderer_fling_count_;
+  }
+
   // |gesture_event_queue_| will forward to OnGestureEventAck when appropriate.
   gesture_event_queue_.ProcessGestureAck(ack_result, type, latency);
 }
diff --git a/content/browser/renderer_host/input/input_router_impl.h b/content/browser/renderer_host/input/input_router_impl.h
index 1abe33b..73f9579 100644
--- a/content/browser/renderer_host/input/input_router_impl.h
+++ b/content/browser/renderer_host/input/input_router_impl.h
@@ -247,6 +247,11 @@ private:
   // to the client_ after all events have been dispatched/acked.
   bool flush_requested_;
 
+  // Whether there are any active flings in the renderer. As the fling
+  // end notification is asynchronous, we use a count rather than a boolean
+  // to avoid races in bookkeeping when starting a new fling.
+  int active_renderer_fling_count_;
+
   TouchEventQueue touch_event_queue_;
   GestureEventQueue gesture_event_queue_;
   TouchActionFilter touch_action_filter_;
diff --git a/content/browser/renderer_host/input/input_router_impl_unittest.cc b/content/browser/renderer_host/input/input_router_impl_unittest.cc
index 83aab38..90ece24 100644
--- a/content/browser/renderer_host/input/input_router_impl_unittest.cc
+++ b/content/browser/renderer_host/input/input_router_impl_unittest.cc
@@ -1601,6 +1601,47 @@ TEST_F(InputRouterImplTest, InputFlush) {
   EXPECT_FALSE(HasPendingEvents());
 }
 
+// Test that the router will call the client's |DidFlush| after all fling
+// animations have completed.
+TEST_F(InputRouterImplTest, InputFlushAfterFling) {
+  EXPECT_FALSE(HasPendingEvents());
+
+  // Simulate a fling.
+  SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
+                       blink::WebGestureDeviceTouchscreen);
+  SimulateGestureEvent(WebInputEvent::GestureFlingStart,
+                       blink::WebGestureDeviceTouchscreen);
+  EXPECT_TRUE(HasPendingEvents());
+
+  // If the fling is unconsumed, the flush is complete.
+  RequestNotificationWhenFlushed();
+  EXPECT_EQ(0U, GetAndResetDidFlushCount());
+  SimulateGestureEvent(WebInputEvent::GestureScrollBegin,
+                       blink::WebGestureDeviceTouchscreen);
+  SendInputEventACK(WebInputEvent::GestureFlingStart,
+                    INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  EXPECT_FALSE(HasPendingEvents());
+  EXPECT_EQ(1U, GetAndResetDidFlushCount());
+
+  // Simulate a second fling.
+  SimulateGestureEvent(WebInputEvent::GestureFlingStart,
+                       blink::WebGestureDeviceTouchscreen);
+  EXPECT_TRUE(HasPendingEvents());
+
+  // If the fling is consumed, the flush is complete only when the renderer
+  // reports that is has ended.
+  RequestNotificationWhenFlushed();
+  EXPECT_EQ(0U, GetAndResetDidFlushCount());
+  SendInputEventACK(WebInputEvent::GestureFlingStart,
+                    INPUT_EVENT_ACK_STATE_CONSUMED);
+  EXPECT_TRUE(HasPendingEvents());
+  EXPECT_EQ(0U, GetAndResetDidFlushCount());
+
+  // The fling end notification should signal that the router is flushed.
+  input_router()->OnMessageReceived(InputHostMsg_DidStopFlinging(0));
+  EXPECT_EQ(1U, GetAndResetDidFlushCount());
+}
+
 // Test that GesturePinchUpdate is handled specially for trackpad
 TEST_F(InputRouterImplTest, TouchpadPinchUpdate) {
   // GesturePinchUpdate for trackpad sends synthetic wheel events.
diff --git a/tools/perf/benchmarks/smoothness.py b/tools/perf/benchmarks/smoothness.py
index 4b20d94..8d3df64 100644
--- a/tools/perf/benchmarks/smoothness.py
+++ b/tools/perf/benchmarks/smoothness.py
@@ -247,7 +247,7 @@ class SmoothnessSimpleMobilePages(benchmark.Benchmark):
     return 'smoothness.simple_mobile_sites'
 
 
-@benchmark.Disabled  # crbug.com/483037
+@benchmark.Enabled('android')
 class SmoothnessFlingSimpleMobilePages(benchmark.Benchmark):
   """Measures rendering statistics for flinging a simple mobile sites page set.
   """