events: Introduce PlatformEventDispatcher and PlatformEventSource.

ui/events/platform/platform_event_source_unittest.cc

Index: ui/events/platform/platform_event_source_unittest.cc
diff --git a/ui/events/platform/platform_event_source_unittest.cc b/ui/events/platform/platform_event_source_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..56aef352af5ea310f1e37eae1f286b4e2031ba5a
--- /dev/null
+++ b/ui/events/platform/platform_event_source_unittest.cc
@@ -0,0 +1,609 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/events/platform/platform_event_source.h"
+
+#include "base/bind.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/events/platform/platform_event_dispatcher.h"
+#include "ui/events/platform/platform_event_observer.h"
+#include "ui/events/platform/scoped_event_dispatcher.h"
+
+namespace ui {
+
+namespace {
+
+scoped_ptr<PlatformEvent> CreatePlatformEvent() {
+  scoped_ptr<PlatformEvent> event(new PlatformEvent());
+  memset(event.get(), 0, sizeof(PlatformEvent));
+  return event.Pass();
+}
+
+template <typename T>
+void DestroyScopedPtr(scoped_ptr<T> object) {}
+
+}  // namespace
+
+class TestPlatformEventSource : public PlatformEventSource {
+ public:
+  TestPlatformEventSource() {}
+  virtual ~TestPlatformEventSource() {}
+
+  uint32_t Dispatch(const PlatformEvent& event) { return DispatchEvent(event); }
+
+  // Dispatches the stream of events, and returns the number of events that are
+  // dispatched before it is requested to stop.
+  size_t DispatchEventStream(const ScopedVector<PlatformEvent>& events) {
+    for (size_t count = 0; count < events.size(); ++count) {
+      uint32_t action = DispatchEvent(*events[count]);
+      if (action & POST_DISPATCH_QUIT_LOOP)
+        return count + 1;
+    }
+    return events.size();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestPlatformEventSource);
+};
+
+class TestPlatformEventDispatcher : public PlatformEventDispatcher {
+ public:
+  TestPlatformEventDispatcher(int id, std::vector<int>* list)
+      : id_(id), list_(list), post_dispatch_action_(POST_DISPATCH_NONE) {
+    PlatformEventSource::GetInstance()->AddPlatformEventDispatcher(this);
+  }
+  virtual ~TestPlatformEventDispatcher() {
+    PlatformEventSource::GetInstance()->RemovePlatformEventDispatcher(this);
+  }
+
+  void set_post_dispatch_action(uint32_t action) {
+    post_dispatch_action_ = action;
+  }
+
+ protected:
+  // PlatformEventDispatcher:
+  virtual bool CanDispatchEvent(const PlatformEvent& event) OVERRIDE {
+    return true;
+  }
+
+  virtual uint32_t DispatchEvent(const PlatformEvent& event) OVERRIDE {
+    list_->push_back(id_);
+    return post_dispatch_action_;
+  }
+
+ private:
+  int id_;
+  std::vector<int>* list_;
+  uint32_t post_dispatch_action_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestPlatformEventDispatcher);
+};
+
+class TestPlatformEventObserver : public PlatformEventObserver {
+ public:
+  TestPlatformEventObserver(int id, std::vector<int>* list)
+      : id_(id), list_(list), consume_event_(false) {
+    PlatformEventSource::GetInstance()->AddPlatformEventObserver(this);
+  }
+  virtual ~TestPlatformEventObserver() {
+    PlatformEventSource::GetInstance()->RemovePlatformEventObserver(this);
+  }
+
+  void set_consume_event(bool consume) { consume_event_ = consume; }
+
+ protected:
+  // PlatformEventObserver:
+  virtual EventStatus WillProcessEvent(const PlatformEvent& event) OVERRIDE {
+    list_->push_back(id_);
+    return consume_event_ ? EVENT_STATUS_HANDLED : EVENT_STATUS_CONTINUE;
+  }
+
+  virtual void DidProcessEvent(const PlatformEvent& event) OVERRIDE {}
+
+ private:
+  int id_;
+  std::vector<int>* list_;
+  bool consume_event_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestPlatformEventObserver);
+};
+
+class PlatformEventTest : public testing::Test {
+ public:
+  PlatformEventTest() {}
+  virtual ~PlatformEventTest() {}
+
+  TestPlatformEventSource* source() { return source_.get(); }
+
+ protected:
+  // testing::Test:
+  virtual void SetUp() OVERRIDE {
+    source_.reset(new TestPlatformEventSource());
+  }
+
+ private:
+  scoped_ptr<TestPlatformEventSource> source_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformEventTest);
+};
+
+// Tests that a dispatcher receives an event.
+TEST_F(PlatformEventTest, DispatcherBasic) {
+  std::vector<int> list_dispatcher;
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  EXPECT_EQ(0u, list_dispatcher.size());
+  {
+    TestPlatformEventDispatcher dispatcher(1, &list_dispatcher);
+
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    source()->Dispatch(*event);
+    ASSERT_EQ(1u, list_dispatcher.size());
+    EXPECT_EQ(1, list_dispatcher[0]);
+  }
+
+  list_dispatcher.clear();
+  event = CreatePlatformEvent();
+  source()->Dispatch(*event);
+  EXPECT_EQ(0u, list_dispatcher.size());
+}
+
+// Tests that dispatchers receive events in the correct order.
+TEST_F(PlatformEventTest, DispatcherOrder) {
+  std::vector<int> list_dispatcher;
+  int sequence[] = {21, 3, 6, 45};
+  ScopedVector<TestPlatformEventDispatcher> dispatchers;
+  for (size_t i = 0; i < arraysize(sequence); ++i) {
+    dispatchers.push_back(
+        new TestPlatformEventDispatcher(sequence[i], &list_dispatcher));
+  }
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  ASSERT_EQ(arraysize(sequence), list_dispatcher.size());
+  EXPECT_EQ(std::vector<int>(sequence, sequence + arraysize(sequence)),
+            list_dispatcher);
+}
+
+// Tests that if a dispatcher consumes the event, the subsequent dispatchers do
+// not receive the event.
+TEST_F(PlatformEventTest, DispatcherConsumesEventToStopDispatch) {
+  std::vector<int> list_dispatcher;
+  TestPlatformEventDispatcher first(12, &list_dispatcher);
+  TestPlatformEventDispatcher second(23, &list_dispatcher);
+
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  ASSERT_EQ(2u, list_dispatcher.size());
+  EXPECT_EQ(12, list_dispatcher[0]);
+  EXPECT_EQ(23, list_dispatcher[1]);
+  list_dispatcher.clear();
+
+  first.set_post_dispatch_action(POST_DISPATCH_STOP_PROPAGATION);
+  event = CreatePlatformEvent();
+  source()->Dispatch(*event);
+  ASSERT_EQ(1u, list_dispatcher.size());
+  EXPECT_EQ(12, list_dispatcher[0]);
+}
+
+// Tests that observers receive events.
+TEST_F(PlatformEventTest, ObserverBasic) {
+  std::vector<int> list_observer;
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  EXPECT_EQ(0u, list_observer.size());
+  {
+    TestPlatformEventObserver observer(31, &list_observer);
+
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    source()->Dispatch(*event);
+    ASSERT_EQ(1u, list_observer.size());
+    EXPECT_EQ(31, list_observer[0]);
+  }
+
+  list_observer.clear();
+  event = CreatePlatformEvent();
+  source()->Dispatch(*event);
+  EXPECT_EQ(0u, list_observer.size());
+}
+
+// Tests that observers receive events in the correct order.
+TEST_F(PlatformEventTest, ObserverOrder) {
+  std::vector<int> list_observer;
+  const int sequence[] = {21, 3, 6, 45};
+  ScopedVector<TestPlatformEventObserver> observers;
+  for (size_t i = 0; i < arraysize(sequence); ++i) {
+    observers.push_back(
+        new TestPlatformEventObserver(sequence[i], &list_observer));
+  }
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  ASSERT_EQ(arraysize(sequence), list_observer.size());
+  EXPECT_EQ(std::vector<int>(sequence, sequence + arraysize(sequence)),
+            list_observer);
+}
+
+// Tests that observers and dispatchers receive events in the correct order.
+TEST_F(PlatformEventTest, DispatcherAndObserverOrder) {
+  std::vector<int> list;
+  TestPlatformEventDispatcher first_d(12, &list);
+  TestPlatformEventObserver first_o(10, &list);
+  TestPlatformEventDispatcher second_d(23, &list);
+  TestPlatformEventObserver second_o(20, &list);
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  const int expected[] = {10, 20, 12, 23};
+  EXPECT_EQ(std::vector<int>(expected, expected + arraysize(expected)), list);
+}
+
+// Tests that an observer can consume an event and stop its dispatch.
+TEST_F(PlatformEventTest, ObserverConsumesEventToStopDispatch) {
+  std::vector<int> list;
+  TestPlatformEventDispatcher first_d(12, &list);
+  TestPlatformEventObserver first_o(10, &list);
+  TestPlatformEventDispatcher second_d(23, &list);
+  TestPlatformEventObserver second_o(20, &list);
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  const int expected[] = {10, 20, 12, 23};
+  EXPECT_EQ(std::vector<int>(expected, expected + arraysize(expected)), list);
+
+  list.clear();
+  first_o.set_consume_event(true);
+  event = CreatePlatformEvent();
+  source()->Dispatch(*event);
+  ASSERT_EQ(1u, list.size());
+  EXPECT_EQ(10, list[0]);
+}
+
+// Tests that an overridden dispatcher receives events before the default
+// dispatchers.
+TEST_F(PlatformEventTest, OverriddenDispatcherBasic) {
+  std::vector<int> list;
+  TestPlatformEventDispatcher dispatcher(10, &list);
+  TestPlatformEventObserver observer(15, &list);
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  ASSERT_EQ(2u, list.size());
+  EXPECT_EQ(15, list[0]);
+  EXPECT_EQ(10, list[1]);
+  list.clear();
+
+  TestPlatformEventDispatcher overriding_dispatcher(20, &list);
+  source()->RemovePlatformEventDispatcher(&overriding_dispatcher);
+  scoped_ptr<ScopedEventDispatcher> handle =
+      source()->OverrideDispatcher(&overriding_dispatcher);
+  source()->Dispatch(*event);
+  ASSERT_EQ(2u, list.size());
+  EXPECT_EQ(15, list[0]);
+  EXPECT_EQ(20, list[1]);
+}
+
+// Tests that an overridden dispatcher can request that the default dispatchers
+// can dispatch the events.
+TEST_F(PlatformEventTest, OverriddenDispatcherInvokeDefaultDispatcher) {
+  std::vector<int> list;
+  TestPlatformEventDispatcher dispatcher(10, &list);
+  TestPlatformEventObserver observer(15, &list);
+  TestPlatformEventDispatcher overriding_dispatcher(20, &list);
+  source()->RemovePlatformEventDispatcher(&overriding_dispatcher);
+  scoped_ptr<ScopedEventDispatcher> handle =
+      source()->OverrideDispatcher(&overriding_dispatcher);
+  overriding_dispatcher.set_post_dispatch_action(POST_DISPATCH_PERFORM_DEFAULT);
+
+  scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+  source()->Dispatch(*event);
+  // First the observer, then the overriding dispatcher, then the default
+  // dispatcher.
+  ASSERT_EQ(3u, list.size());
+  EXPECT_EQ(15, list[0]);
+  EXPECT_EQ(20, list[1]);
+  EXPECT_EQ(10, list[2]);
+  list.clear();
+
+  // Install a second overriding dispatcher.
+  TestPlatformEventDispatcher second_overriding(50, &list);
+  source()->RemovePlatformEventDispatcher(&second_overriding);
+  scoped_ptr<ScopedEventDispatcher> second_override_handle =
+      source()->OverrideDispatcher(&second_overriding);
+  source()->Dispatch(*event);
+  ASSERT_EQ(2u, list.size());
+  EXPECT_EQ(15, list[0]);
+  EXPECT_EQ(50, list[1]);
+  list.clear();
+
+  second_overriding.set_post_dispatch_action(POST_DISPATCH_PERFORM_DEFAULT);
+  source()->Dispatch(*event);
+  // First the observer, then the second overriding dispatcher, then the default
+  // dispatcher.
+  ASSERT_EQ(3u, list.size());
+  EXPECT_EQ(15, list[0]);
+  EXPECT_EQ(50, list[1]);
+  EXPECT_EQ(10, list[2]);
+}
+
+// Provides mechanism for running tests from inside an active message-loop.
+class PlatformEventTestWithMessageLoop : public PlatformEventTest {
+ public:
+  PlatformEventTestWithMessageLoop() {}
+  virtual ~PlatformEventTestWithMessageLoop() {}
+
+  void Run() {
+    message_loop_.PostTask(
+        FROM_HERE,
+        base::Bind(&PlatformEventTestWithMessageLoop::RunTest,
+                   base::Unretained(this)));
+    message_loop_.Run();
+  }
+
+ protected:
+  void RunTest() {
+    RunTestImpl();
+    message_loop_.Quit();
+  }
+
+  virtual void RunTestImpl() = 0;
+
+ private:
+  base::MessageLoopForUI message_loop_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformEventTestWithMessageLoop);
+};
+
+#define RUN_TEST_IN_MESSAGE_LOOP(name) \
+  TEST_F(name, Run) { Run(); }
+
+// Tests that a ScopedEventDispatcher restores the previous dispatcher when
+// destroyed.
+class ScopedDispatcherRestoresAfterDestroy
+    : public PlatformEventTestWithMessageLoop {
+ public:
+  // PlatformEventTestWithMessageLoop:
+  virtual void RunTestImpl() OVERRIDE {
+    std::vector<int> list;
+    TestPlatformEventDispatcher dispatcher(10, &list);
+    TestPlatformEventObserver observer(15, &list);
+
+    TestPlatformEventDispatcher first_overriding(20, &list);
+    source()->RemovePlatformEventDispatcher(&first_overriding);
+    scoped_ptr<ScopedEventDispatcher> first_override_handle =
+        source()->OverrideDispatcher(&first_overriding);
+
+    // Install a second overriding dispatcher.
+    TestPlatformEventDispatcher second_overriding(50, &list);
+    source()->RemovePlatformEventDispatcher(&second_overriding);
+    scoped_ptr<ScopedEventDispatcher> second_override_handle =
+        source()->OverrideDispatcher(&second_overriding);
+
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list.size());
+    EXPECT_EQ(15, list[0]);
+    EXPECT_EQ(50, list[1]);
+    list.clear();
+
+    second_override_handle.reset();
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list.size());
+    EXPECT_EQ(15, list[0]);
+    EXPECT_EQ(20, list[1]);
+  }
+};
+
+RUN_TEST_IN_MESSAGE_LOOP(ScopedDispatcherRestoresAfterDestroy)
+
+// This dispatcher destroys the handle to the ScopedEventDispatcher when
+// dispatching an event.
+class DestroyScopedHandleDispatcher : public TestPlatformEventDispatcher {
+ public:
+  DestroyScopedHandleDispatcher(int id, std::vector<int>* list)
+      : TestPlatformEventDispatcher(id, list) {}
+  virtual ~DestroyScopedHandleDispatcher() {}
+
+  void SetScopedHandle(scoped_ptr<ScopedEventDispatcher> handler) {
+    handler_ = handler.Pass();
+  }
+
+ private:
+  // PlatformEventDispatcher:
+  virtual bool CanDispatchEvent(const PlatformEvent& event) OVERRIDE {
+    return true;
+  }
+
+  virtual uint32_t DispatchEvent(const PlatformEvent& event) OVERRIDE {
+    handler_.reset();
+    return TestPlatformEventDispatcher::DispatchEvent(event);
+  }
+
+  scoped_ptr<ScopedEventDispatcher> handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(DestroyScopedHandleDispatcher);
+};
+
+// Tests that resetting an overridden dispatcher causes the nested message-loop
+// iteration to stop and the rest of the events are dispatched in the next
+// iteration.
+class DestroyedNestedOverriddenDispatcherQuitsNestedLoopIteration
+    : public PlatformEventTestWithMessageLoop {
+ public:
+  void NestedTask(std::vector<int>* list,
+                  TestPlatformEventDispatcher* dispatcher) {
+    ScopedVector<PlatformEvent> events;
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    events.push_back(event.release());
+    event = CreatePlatformEvent();
+    events.push_back(event.release());
+
+    // Attempt to dispatch a couple of events. Dispatching the first event will
+    // have terminated the ScopedEventDispatcher object, which will terminate
+    // the current iteration of the message-loop.
+    size_t count = source()->DispatchEventStream(events);
+    EXPECT_EQ(1u, count);
+    ASSERT_EQ(2u, list->size());
+    EXPECT_EQ(15, (*list)[0]);
+    EXPECT_EQ(20, (*list)[1]);
+    list->clear();
+
+    ASSERT_LT(count, events.size());
+    events.erase(events.begin(), events.begin() + count);
+
+    count = source()->DispatchEventStream(events);
+    EXPECT_EQ(1u, count);
+    ASSERT_EQ(2u, list->size());
+    EXPECT_EQ(15, (*list)[0]);
+    EXPECT_EQ(10, (*list)[1]);
+    list->clear();
+
+    // Terminate the message-loop.
+    base::MessageLoopForUI::current()->QuitNow();
+  }
+
+  // PlatformEventTestWithMessageLoop:
+  virtual void RunTestImpl() OVERRIDE {
+    std::vector<int> list;
+    TestPlatformEventDispatcher dispatcher(10, &list);
+    TestPlatformEventObserver observer(15, &list);
+
+    DestroyScopedHandleDispatcher overriding(20, &list);
+    source()->RemovePlatformEventDispatcher(&overriding);
+    scoped_ptr<ScopedEventDispatcher> override_handle =
+        source()->OverrideDispatcher(&overriding);
+
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list.size());
+    EXPECT_EQ(15, list[0]);
+    EXPECT_EQ(20, list[1]);
+    list.clear();
+
+    overriding.SetScopedHandle(override_handle.Pass());
+    base::RunLoop run_loop;
+    base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
+    base::MessageLoopForUI::ScopedNestableTaskAllower allow_nested(loop);
+    loop->PostTask(
+        FROM_HERE,
+        base::Bind(
+            &DestroyedNestedOverriddenDispatcherQuitsNestedLoopIteration::
+                NestedTask,
+            base::Unretained(this),
+            base::Unretained(&list),
+            base::Unretained(&overriding)));
+    run_loop.Run();
+
+    // Dispatching the event should now reach the default dispatcher.
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list.size());
+    EXPECT_EQ(15, list[0]);
+    EXPECT_EQ(10, list[1]);
+  }
+};
+
+RUN_TEST_IN_MESSAGE_LOOP(
+    DestroyedNestedOverriddenDispatcherQuitsNestedLoopIteration)
+
+// Tests that resetting an overridden dispatcher, and installing another
+// overridden dispatcher before the nested message-loop completely unwinds
+// function correctly.
+class ConsecutiveOverriddenDispatcherInTheSameMessageLoopIteration
+    : public PlatformEventTestWithMessageLoop {
+ public:
+  void NestedTask(scoped_ptr<ScopedEventDispatcher> dispatch_handle,
+                  std::vector<int>* list) {
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list->size());
+    EXPECT_EQ(15, (*list)[0]);
+    EXPECT_EQ(20, (*list)[1]);
+    list->clear();
+
+    // Reset the override dispatcher. This should restore the default
+    // dispatcher.
+    dispatch_handle.reset();
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list->size());
+    EXPECT_EQ(15, (*list)[0]);
+    EXPECT_EQ(10, (*list)[1]);
+    list->clear();
+
+    // Install another override-dispatcher.
+    DestroyScopedHandleDispatcher second_overriding(70, list);
+    source()->RemovePlatformEventDispatcher(&second_overriding);
+    scoped_ptr<ScopedEventDispatcher> second_override_handle =
+        source()->OverrideDispatcher(&second_overriding);
+
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list->size());
+    EXPECT_EQ(15, (*list)[0]);
+    EXPECT_EQ(70, (*list)[1]);
+    list->clear();
+
+    second_overriding.SetScopedHandle(second_override_handle.Pass());
+    second_overriding.set_post_dispatch_action(POST_DISPATCH_QUIT_LOOP);
+    base::RunLoop run_loop;
+    base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
+    base::MessageLoopForUI::ScopedNestableTaskAllower allow_nested(loop);
+    loop->PostTask(
+        FROM_HERE,
+        base::Bind(base::IgnoreResult(&TestPlatformEventSource::Dispatch),
+                   base::Unretained(source()),
+                   *event));
+    run_loop.Run();
+    ASSERT_EQ(2u, list->size());
+    EXPECT_EQ(15, (*list)[0]);
+    EXPECT_EQ(70, (*list)[1]);
+    list->clear();
+
+    // Terminate the message-loop.
+    base::MessageLoopForUI::current()->QuitNow();
+  }
+
+  // PlatformEventTestWithMessageLoop:
+  virtual void RunTestImpl() OVERRIDE {
+    std::vector<int> list;
+    TestPlatformEventDispatcher dispatcher(10, &list);
+    TestPlatformEventObserver observer(15, &list);
+
+    TestPlatformEventDispatcher overriding(20, &list);
+    source()->RemovePlatformEventDispatcher(&overriding);
+    scoped_ptr<ScopedEventDispatcher> override_handle =
+        source()->OverrideDispatcher(&overriding);
+
+    scoped_ptr<PlatformEvent> event(CreatePlatformEvent());
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list.size());
+    EXPECT_EQ(15, list[0]);
+    EXPECT_EQ(20, list[1]);
+    list.clear();
+
+    // Start a nested message-loop, and destroy |override_handle| in the nested
+    // loop. That should terminate the nested loop, restore the previous
+    // dispatchers, and return control to this function.
+    base::RunLoop run_loop;
+    base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
+    base::MessageLoopForUI::ScopedNestableTaskAllower allow_nested(loop);
+    loop->PostTask(
+        FROM_HERE,
+        base::Bind(
+            &ConsecutiveOverriddenDispatcherInTheSameMessageLoopIteration::
+                NestedTask,
+            base::Unretained(this),
+            base::Passed(&override_handle),
+            base::Unretained(&list)));
+    run_loop.Run();
+
+    // Dispatching the event should now reach the default dispatcher.
+    source()->Dispatch(*event);
+    ASSERT_EQ(2u, list.size());
+    EXPECT_EQ(15, list[0]);
+    EXPECT_EQ(10, list[1]);
+  }
+};
+
+RUN_TEST_IN_MESSAGE_LOOP(
+    ConsecutiveOverriddenDispatcherInTheSameMessageLoopIteration)
+
+}  // namespace ui