Fix flakey test: BasicSelectionIsolatedScrollMainframe on TSAN/Linux

This CL is a speculative fix for the observed flakiness of this
test on TSAN linux. It seems that the old method of waiting for the
scroll data to propagate back to the browser, namely using a
UpdateResizeParamsMessageFilter to wait for the frame rects to
change, is no longer sufficient to synchronize. It's also necessary to
wait for the child-frame to draw its compositor frame so that the
transform functions used in TouchSelectionControllerClientChildFrame's
DidScroll() method will work properly (they rely on the compositor
surfaces to reflect the scroll changes).

Bug: 805017
Change-Id: I69ec3f318af8adb224d7fb54be1d00ec3c6caae8
Reviewed-on: https://chromium-review.googlesource.com/889864
Commit-Queue: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532661}

content/browser/renderer_host/input/touch_selection_controller_client_aura_browsertest.cc

@@ -233,6 +233,42 @@ IN_PROC_BROWSER_TEST_F(TouchSelectionControllerClientAuraTest, BasicSelection) {
   EXPECT_TRUE(ui::TouchSelectionMenuRunner::GetInstance()->IsRunning());
 }
 
+class GestureLongPressWaiter : public RenderWidgetHost::InputEventObserver {
+ public:
+  GestureLongPressWaiter(RenderWidgetHost* rwh)
+      : rwh_(static_cast<RenderWidgetHostImpl*>(rwh)->GetWeakPtr()),
+        gesture_long_press_seen_(false) {
+    rwh->AddInputEventObserver(this);
+  }
+  ~GestureLongPressWaiter() override {
+    if (rwh_)
+      rwh_->RemoveInputEventObserver(this);
+  }
+
+  void OnInputEventAck(InputEventAckSource,
+                       InputEventAckState,
+                       const blink::WebInputEvent& event) override {
+    if (event.GetType() == blink::WebInputEvent::kGestureLongPress) {
+      gesture_long_press_seen_ = true;
+      if (run_loop_)
+        run_loop_->Quit();
+    }
+  }
+
+  void Wait() {
+    if (gesture_long_press_seen_)
+      return;
+    run_loop_.reset(new base::RunLoop);
+    run_loop_->Run();
+    run_loop_.reset();
+  }
+
+ private:
+  base::WeakPtr<RenderWidgetHostImpl> rwh_;
+  std::unique_ptr<base::RunLoop> run_loop_;
+  bool gesture_long_press_seen_;
+};
+
 class TouchSelectionControllerClientAuraSiteIsolationTest
     : public TouchSelectionControllerClientAuraTest,
       public testing::WithParamInterface<bool> {
@@ -248,14 +284,21 @@ class TouchSelectionControllerClientAuraSiteIsolationTest
     ASSERT_TRUE(embedded_test_server()->Start());
   }
 
-  void SelectWithLongPress(gfx::Point point) {
+  void SelectWithLongPress(gfx::Point point,
+                           RenderWidgetHostViewBase* expected_target) {
     // Get main frame view for event insertion.
     RenderWidgetHostViewAura* main_view = GetRenderWidgetHostViewAura();
 
     SendTouch(main_view, ui::ET_TOUCH_PRESSED, point);
     SendTouch(main_view, ui::ET_TOUCH_RELEASED, point);
     SendGestureTap(main_view, point);
+
+    // Since our hit-testing is now asynchronous, wait for the Ack to come
+    // back before proceeding.
+    GestureLongPressWaiter long_press_waiter(
+        expected_target->GetRenderWidgetHost());
     SendGestureLongPress(main_view, point);
+    long_press_waiter.Wait();
   }
 
   void SimpleTap(gfx::Point point) {
@@ -406,7 +449,7 @@ IN_PROC_BROWSER_TEST_P(TouchSelectionControllerClientAuraSiteIsolationTest,
   parent_selection_controller_client->InitWaitForSelectionEvent(
       ui::SELECTION_HANDLES_SHOWN);
 
-  SelectWithLongPress(gfx::Point(point_f.x(), point_f.y()));
+  SelectWithLongPress(gfx::Point(point_f.x(), point_f.y()), child_view);
 
   parent_selection_controller_client->Wait();
 
@@ -523,7 +566,7 @@ IN_PROC_BROWSER_TEST_P(TouchSelectionControllerClientAuraSiteIsolationTest,
   parent_selection_controller_client->InitWaitForSelectionEvent(
       ui::SELECTION_HANDLES_SHOWN);
 
-  SelectWithLongPress(gfx::Point(point_f.x(), point_f.y()));
+  SelectWithLongPress(gfx::Point(point_f.x(), point_f.y()), child_view);
 
   parent_selection_controller_client->Wait();
 
@@ -587,6 +630,14 @@ IN_PROC_BROWSER_TEST_P(TouchSelectionControllerClientAuraSiteIsolationTest,
 
   // Make sure we wait for the scroll to actually happen.
   filter->WaitForRect();
+  // Since the check below that compares the scroll_delta to the actual handle
+  // movement requires use of TransformPointToRootCoordSpaceF() in
+  // TouchSelectionControllerClientChildFrame::DidScroll(), we need to
+  // make sure the post-scroll frames have rendered before the transform
+  // can be trusted. This may point out a general concern with the timing
+  // of the main-frame's did-stop-flinging IPC and the rendering of the
+  // child frame's compositor frame.
+  child_frame_stable_observer.WaitUntilStable();
 
   // End scrolling: touch handles should re-appear.
   ui::GestureEventDetails scroll_end_details(ui::ET_GESTURE_SCROLL_END);