input: Change how synthesized events are dispatched in telemetry tests.

content/browser/renderer_host/input/synthetic_gesture_controller.cc

Index: content/browser/renderer_host/input/synthetic_gesture_controller.cc
diff --git a/content/browser/renderer_host/input/synthetic_gesture_controller.cc b/content/browser/renderer_host/input/synthetic_gesture_controller.cc
index 9e5bc84403eb18e01f09e43b26b9db51fbd20211..51c28aa406042f57fed6562efd9c550582f7a982 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_controller.cc
+++ b/content/browser/renderer_host/input/synthetic_gesture_controller.cc
@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "content/browser/renderer_host/input/synthetic_gesture_target.h"
 #include "content/common/input/synthetic_smooth_scroll_gesture_params.h"
@@ -15,8 +16,11 @@
 namespace content {
 
 SyntheticGestureController::SyntheticGestureController(
-    std::unique_ptr<SyntheticGestureTarget> gesture_target)
-    : gesture_target_(std::move(gesture_target)) {}
+    std::unique_ptr<SyntheticGestureTarget> gesture_target,
+    BeginFrameRequestCallback begin_frame_callback)
+    : gesture_target_(std::move(gesture_target)),
+      begin_frame_callback_(std::move(begin_frame_callback)),
+      weak_ptr_factory_(this) {}
 
 SyntheticGestureController::~SyntheticGestureController() {}
 
@@ -34,51 +38,44 @@ void SyntheticGestureController::QueueSyntheticGesture(
     StartGesture(*pending_gesture_queue_.FrontGesture());
 }
 
-void SyntheticGestureController::Flush(base::TimeTicks timestamp) {
+void SyntheticGestureController::OnBeginFrame() {
+  // TODO(sad): Instead of dispatching the events immediately, dispatch after an
+  // offset.
+  DispatchNextEvent();
+}
+
+bool SyntheticGestureController::DispatchNextEvent(base::TimeTicks timestamp) {
   TRACE_EVENT0("input", "SyntheticGestureController::Flush");
   if (pending_gesture_queue_.IsEmpty())
-    return;
-
-  if (pending_gesture_result_)
-    return;
+    return false;
 
-  SyntheticGesture* gesture = pending_gesture_queue_.FrontGesture();
   SyntheticGesture::Result result =
-      gesture->ForwardInputEvents(timestamp, gesture_target_.get());
+      pending_gesture_queue_.FrontGesture()->ForwardInputEvents(
+          timestamp, gesture_target_.get());
 
   if (result == SyntheticGesture::GESTURE_RUNNING) {
-    gesture_target_->SetNeedsFlush();
-    return;
+    begin_frame_callback_.Run(
+        base::BindOnce(&SyntheticGestureController::OnBeginFrame,
+                       weak_ptr_factory_.GetWeakPtr()));
+    return true;
   }
 
-  // It's possible that all events generated by the gesture have been fully
-  // dispatched at this point, in which case |OnDidFlushInput()| was called
-  // before |pending_gesture_result_| was initialized. Requesting another flush
-  // will trigger the necessary gesture-ending call to |OnDidFlushInput()|.
-  pending_gesture_result_.reset(new SyntheticGesture::Result(result));
-  gesture_target_->SetNeedsFlush();
-}
-
-void SyntheticGestureController::OnDidFlushInput() {
-  if (!pending_gesture_result_)
-    return;
-
-  DCHECK(!pending_gesture_queue_.IsEmpty());
-  auto pending_gesture_result = std::move(pending_gesture_result_);
   StopGesture(*pending_gesture_queue_.FrontGesture(),
-              pending_gesture_queue_.FrontCallback(),
-              *pending_gesture_result);
+              pending_gesture_queue_.FrontCallback(), result);
   pending_gesture_queue_.Pop();
-
-  if (!pending_gesture_queue_.IsEmpty())
-    StartGesture(*pending_gesture_queue_.FrontGesture());
+  if (pending_gesture_queue_.IsEmpty())
+    return false;
+  StartGesture(*pending_gesture_queue_.FrontGesture());
+  return true;
 }
 
 void SyntheticGestureController::StartGesture(const SyntheticGesture& gesture) {
   TRACE_EVENT_ASYNC_BEGIN0("input,benchmark",
                            "SyntheticGestureController::running",
                            &gesture);
-  gesture_target_->SetNeedsFlush();
+  begin_frame_callback_.Run(
+      base::BindOnce(&SyntheticGestureController::OnBeginFrame,
+                     weak_ptr_factory_.GetWeakPtr()));
 }
 
 void SyntheticGestureController::StopGesture(