Fix SubframeGestureEventRouting in mash

- Add a ScopedAllow helper class that SystemEventRewriter allows
  event to pass through when there are instances of it;
- Use ScopedAllow helper to allow fake gesture events to pass
  through under mash;

Bug: 884360
Change-Id: I940398b0920505743ad7adbe08e12e1394fb55c0
Reviewed-on: https://chromium-review.googlesource.com/c/1292400Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605496}

chrome/browser/ui/views/frame/browser_non_client_frame_view_ash_browsertest.cc

@@ -78,6 +78,7 @@
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/ws/public/mojom/window_tree_constants.mojom.h"
 #include "ui/aura/client/aura_constants.h"
+#include "ui/aura/event_injector.h"
 #include "ui/aura/test/env_test_helper.h"
 #include "ui/base/class_property.h"
 #include "ui/base/hit_test.h"
@@ -238,6 +239,15 @@ class ImmersiveModeTester : public ImmersiveModeController::Observer {
   DISALLOW_COPY_AND_ASSIGN(ImmersiveModeTester);
 };
 
+// Update mouse location of aura::Env by injecting a mouse move event.
+// EventInjector is used so that the Window Service side code under mash sees
+// the updated mouse location as well.
+void UpdateMouseLocation(aura::Window* window, const gfx::Point& location) {
+  ui::MouseEvent event(ui::ET_MOUSE_MOVED, location, location,
+                       ui::EventTimeForNow(), ui::EF_NONE, 0);
+  aura::EventInjector().Inject(window->GetHost(), &event);
+}
+
 }  // namespace
 
 using views::Widget;
@@ -304,7 +314,10 @@ IN_PROC_BROWSER_TEST_P(BrowserNonClientFrameViewAshTest,
 }
 
 IN_PROC_BROWSER_TEST_P(BrowserNonClientFrameViewAshTest, ImmersiveFullscreen) {
-  aura::test::EnvTestHelper().SetAlwaysUseLastMouseLocation(true);
+  // Move mouse cursor beyond immersive UI to avoid affecting tests.
+  UpdateMouseLocation(browser()->window()->GetNativeWindow(),
+                      gfx::Point(0, 100));
+
   BrowserView* browser_view = BrowserView::GetBrowserViewForBrowser(browser());
   content::WebContents* web_contents = browser_view->GetActiveWebContents();
   BrowserNonClientFrameViewAsh* frame_view = GetFrameViewAsh(browser_view);
@@ -515,9 +528,14 @@ class ImmersiveModeBrowserViewTest
   ImmersiveModeBrowserViewTest() = default;
   ~ImmersiveModeBrowserViewTest() override = default;
 
+  // TopChromeMdParamTest<InProcessBrowserTest>:
   void PreRunTestOnMainThread() override {
     InProcessBrowserTest::PreRunTestOnMainThread();
-    aura::test::EnvTestHelper().SetAlwaysUseLastMouseLocation(true);
+
+    // Move mouse cursor beyond immersive UI to avoid affecting tests.
+    UpdateMouseLocation(browser()->window()->GetNativeWindow(),
+                        gfx::Point(0, 100));
+
     BrowserView::SetDisableRevealerDelayForTesting(true);
   }
 

content/browser/site_per_process_hit_test_browsertest.cc

@@ -674,14 +674,37 @@ class SetMouseCaptureInterceptor
 // that might otherwise cause unpredictable behaviour in tests.
 class SystemEventRewriter : public ui::EventRewriter {
  public:
+  // Helper class to allow events to pass through for the lifetime of the
+  // object. Use this when tests generate events. This is needed under mash
+  // because the generate events reach SystemEventRewriter and will be dropped
+  // if there is no ScopedAllow instance.
+  // Note that allowing system events can cause flakiness in browser tests that
+  // don't expect them.
+  class ScopedAllow {
+   public:
+    explicit ScopedAllow(SystemEventRewriter* rewriter) : rewriter_(rewriter) {
+      ++rewriter_->num_of_scoped_allows_;
+    }
+    ~ScopedAllow() {
+      DCHECK_GT(rewriter_->num_of_scoped_allows_, 0);
+      --rewriter_->num_of_scoped_allows_;
+    }
+
+   private:
+    SystemEventRewriter* const rewriter_;
+
+    DISALLOW_COPY_AND_ASSIGN(ScopedAllow);
+  };
+
   SystemEventRewriter() = default;
-  ~SystemEventRewriter() override {}
+  ~SystemEventRewriter() override = default;
 
  private:
   ui::EventRewriteStatus RewriteEvent(
       const ui::Event& event,
       std::unique_ptr<ui::Event>* new_event) override {
-    return ui::EVENT_REWRITE_DISCARD;
+    return num_of_scoped_allows_ ? ui::EVENT_REWRITE_CONTINUE
+                                 : ui::EVENT_REWRITE_DISCARD;
   }
 
   ui::EventRewriteStatus NextDispatchEvent(
@@ -691,6 +714,10 @@ class SystemEventRewriter : public ui::EventRewriter {
     return ui::EVENT_REWRITE_CONTINUE;
   }
 
+  // Count of ScopedAllow objects. When it is greater than 0, events are allowed
+  // to pass. Otherwise, they are discarded.
+  int num_of_scoped_allows_ = 0;
+
   DISALLOW_COPY_AND_ASSIGN(SystemEventRewriter);
 };
 #endif
@@ -707,11 +734,11 @@ class SitePerProcessHitTestBrowserTest
   void PreRunTestOnMainThread() override {
     SitePerProcessBrowserTest::PreRunTestOnMainThread();
     // Disable system mouse events, which can interfere with tests.
-    shell()->window()->GetHost()->AddEventRewriter(&event_rewriter);
+    shell()->window()->GetHost()->AddEventRewriter(&event_rewriter_);
   }
 
   void PostRunTestOnMainThread() override {
-    shell()->window()->GetHost()->RemoveEventRewriter(&event_rewriter);
+    shell()->window()->GetHost()->RemoveEventRewriter(&event_rewriter_);
     SitePerProcessBrowserTest::PostRunTestOnMainThread();
   }
 #endif
@@ -732,7 +759,7 @@ class SitePerProcessHitTestBrowserTest
 
   base::test::ScopedFeatureList feature_list_;
 #if defined(USE_AURA)
-  SystemEventRewriter event_rewriter;
+  SystemEventRewriter event_rewriter_;
 #endif
 };
 
@@ -3671,6 +3698,10 @@ IN_PROC_BROWSER_TEST_P(SitePerProcessHitTestBrowserTest,
   InputEventAckWaiter ack_waiter(child_frame_host->GetRenderWidgetHost(),
                                  blink::WebInputEvent::kGestureTap);
 
+#if defined(USE_AURA)
+  // Allows the gesture events to go through under mash.
+  SystemEventRewriter::ScopedAllow scoped_allow(&event_rewriter_);
+#endif
   render_widget_host->QueueSyntheticGesture(
       std::move(gesture), base::BindOnce([](SyntheticGesture::Result result) {
         EXPECT_EQ(SyntheticGesture::GESTURE_FINISHED, result);

testing/buildbot/filters/chromeos.single_process_mash.content_browsertests.filter

@@ -19,7 +19,6 @@
 # or RenderWidgetHostMouseEventMonitor::EventWasReceived fails.
 # https://crbug.com/884360
 -SitePerProcessHitTestBrowserTest.CrossProcessTooltipTest*
--SitePerProcessHitTestBrowserTest.SubframeGestureEventRouting*
 
 
 # Flaky. https://crbug.com/889878