Revert "back gesture: Disable back gesture for {touch-action:none} web pages/apps."

This reverts commit 926cd1f5.

Reason for revert: Flakiness in BackGestureBrowserTest.PreventDefault

Three failures observed on linux-chromeos-rel: https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-rel

https://chromium-swarm.appspot.com/task?id=4c8d35366f7d4710#BackGestureBrowserTest.PreventDefault,BackGestureBrowserTest.TouchActions,DemoSetupArcSupportedTest.ShowOfflineSetupOptionOnNetworkList,NetworkQualityTrackerBrowserTest.SimulateNetworkServiceCrash,SwitchAccessPredicateTest.LeafPredicate,TopControlsSlideControllerTest.DisplayRotation

../../chrome/browser/ui/ash/back_gesture_browsertest.cc:210: Failure
Value of: recorder.HasReceivedEvent(ui::EventType::ET_KEY_PRESSED)
  Actual: true
Expected: false
Stack trace:
#0 0x5585e4320fef BackGestureBrowserTest_PreventDefault_Test::RunTestOnMainThread()
#1 0x5585e7da383d content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#2 0x5585e7900459 ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#3 0x5585e78ff599 ChromeBrowserMainParts::PreMainMessageLoopRun()
#4 0x5585e4a12dd9 chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun()
#5 0x5585e5c7fd84 content::BrowserMainLoop::PreMainMessageLoopRun()
#6 0x5585e6079033 content::StartupTaskRunner::RunAllTasksNow()
#7 0x5585e5c7ed8a content::BrowserMainLoop::CreateStartupTasks()
#8 0x5585e5c81611 content::BrowserMainRunnerImpl::Initialize()
#9 0x5585e5c7d3ad content::BrowserMain()
#10 0x5585e7384f2d content::ContentMainRunnerImpl::RunServiceManager()
#11 0x5585e73849b7 content::ContentMainRunnerImpl::Run()
#12 0x5585e99d13d5 service_manager::Main()
#13 0x5585e67835d4 content::ContentMain()
#14 0x5585e7da33ba content::BrowserTestBase::SetUp()
#15 0x5585e77dca3a InProcessBrowserTest::SetUp()

Original change's description:
> back gesture: Disable back gesture for {touch-action:none} web pages/apps.
> 
> Bug: 1063144
> Change-Id: I85379cc2f4aded28ac9eefb09e2086d446f42168
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2166360
> Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
> Reviewed-by: Scott Violet <sky@chromium.org>
> Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
> Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#773852}

TBR=sky@chromium.org,xdai@chromium.org,dtapuska@chromium.org,afakhry@chromium.org

Change-Id: I5123a071659d23d7731a55d1420442c9b878b8bd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1063144
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225764Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
Commit-Queue: Thiemo Nagel <tnagel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774078}

ash/shell_delegate.cc

@@ -6,14 +6,6 @@
 
 namespace ash {
 
-bool ShellDelegate::AllowDefaultTouchActions(gfx::NativeWindow window) {
-  return true;
-}
-
-bool ShellDelegate::ShouldWaitForTouchPressAck(gfx::NativeWindow window) {
-  return false;
-}
-
 bool ShellDelegate::IsTabDrag(const ui::OSExchangeData& drop_data) {
   return false;
 }

ash/shell_delegate.h

@@ -58,16 +58,6 @@ class ASH_EXPORT ShellDelegate {
   // Check whether the current tab of the browser window can go back.
   virtual bool CanGoBack(gfx::NativeWindow window) const = 0;
 
-  // Returns true if |window| allows default touch behaviors. If false, it means
-  // no default touch behavior is allowed (i.e., the touch action of window is
-  // cc::TouchAction::kNone). This function is used by BackGestureEventHandler
-  // to decide if we can perform the system default back gesture.
-  virtual bool AllowDefaultTouchActions(gfx::NativeWindow window);
-
-  // Returns true if we should wait for touch press ack when deciding if back
-  // gesture can be performed.
-  virtual bool ShouldWaitForTouchPressAck(gfx::NativeWindow window);
-
   // Checks whether a drag-drop operation is a tab drag.
   virtual bool IsTabDrag(const ui::OSExchangeData& drop_data);
 

ash/wm/gestures/back_gesture/back_gesture_event_handler.cc

@@ -13,7 +13,6 @@
 #include "ash/session/session_controller_impl.h"
 #include "ash/shelf/contextual_tooltip.h"
 #include "ash/shell.h"
-#include "ash/shell_delegate.h"
 #include "ash/wm/gestures/back_gesture/back_gesture_affordance.h"
 #include "ash/wm/gestures/back_gesture/back_gesture_contextual_nudge_controller_impl.h"
 #include "ash/wm/overview/overview_controller.h"
@@ -27,7 +26,6 @@
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/window.h"
 #include "ui/wm/core/coordinate_conversion.h"
-#include "ui/wm/core/window_util.h"
 
 namespace ash {
 
@@ -172,20 +170,7 @@ void BackGestureEventHandler::OnDisplayMetricsChanged(
   }
 }
 
-void BackGestureEventHandler::OnGestureEvent(ui::GestureEvent* event) {
-  if (should_wait_for_touch_ack_) {
-    aura::Window* target = static_cast<aura::Window*>(event->target());
-    gfx::Point screen_location = event->location();
-    ::wm::ConvertPointToScreen(target, &screen_location);
-    if (MaybeHandleBackGesture(event, screen_location))
-      event->StopPropagation();
-
-    // Reset |should_wait_for_touch_ack_| for the last gesture event in the
-    // sequence.
-    if (event->type() == ui::ET_GESTURE_END)
-      should_wait_for_touch_ack_ = false;
-  }
-}
+void BackGestureEventHandler::OnGestureEvent(ui::GestureEvent* event) {}
 
 void BackGestureEventHandler::OnTouchEvent(ui::TouchEvent* event) {
   // Do not handle PEN and ERASER events for back gesture. PEN events can come
@@ -223,6 +208,14 @@ void BackGestureEventHandler::OnTouchEvent(ui::TouchEvent* event) {
   }
   last_touch_point_ = event->location();
 
+  ui::TouchEvent touch_event_copy = *event;
+  if (!gesture_provider_.OnTouchEvent(&touch_event_copy))
+    return;
+
+  gesture_provider_.OnTouchEventAck(
+      touch_event_copy.unique_event_id(), /*event_consumed=*/false,
+      /*is_source_touch_event_set_non_blocking=*/false);
+
   // Get the event target from TouchEvent since target of the GestureEvent
   // from GetAndResetPendingGestures is nullptr. The coordinate conversion is
   // done outside the loop as the previous gesture events in a sequence may
@@ -233,28 +226,11 @@ void BackGestureEventHandler::OnTouchEvent(ui::TouchEvent* event) {
   aura::Window* target = static_cast<aura::Window*>(event->target());
   gfx::Point screen_location = event->location();
   ::wm::ConvertPointToScreen(target, &screen_location);
-
-  if (event->type() == ui::ET_TOUCH_PRESSED &&
-      ShouldWaitForTouchPressAck(screen_location)) {
-    should_wait_for_touch_ack_ = true;
-    return;
-  }
-
-  if (!should_wait_for_touch_ack_) {
-    ui::TouchEvent touch_event_copy = *event;
-    if (!gesture_provider_.OnTouchEvent(&touch_event_copy))
-      return;
-
-    gesture_provider_.OnTouchEventAck(
-        touch_event_copy.unique_event_id(), /*event_consumed=*/false,
-        /*is_source_touch_event_set_non_blocking=*/false);
-
-    std::vector<std::unique_ptr<ui::GestureEvent>> gestures =
-        gesture_provider_.GetAndResetPendingGestures();
-    for (const auto& gesture : gestures) {
-      if (MaybeHandleBackGesture(gesture.get(), screen_location))
-        event->StopPropagation();
-    }
+  const std::vector<std::unique_ptr<ui::GestureEvent>> gestures =
+      gesture_provider_.GetAndResetPendingGestures();
+  for (const auto& gesture : gestures) {
+    if (MaybeHandleBackGesture(gesture.get(), screen_location))
+      event->StopPropagation();
   }
 }
 
@@ -410,8 +386,6 @@ bool BackGestureEventHandler::CanStartGoingBack(
   if (!top_window && !shell->overview_controller()->InOverviewSession())
     return false;
 
-  // If the event location falls into the window's gesture exclusion zone, do
-  // not handle it.
   for (aura::Window* window = top_window; window; window = window->parent()) {
     SkRegion* gesture_exclusion =
         window->GetProperty(kSystemGestureExclusionKey);
@@ -425,10 +399,6 @@ bool BackGestureEventHandler::CanStartGoingBack(
     }
   }
 
-  // If the target window does not allow touch action, do not handle it.
-  if (!Shell::Get()->shell_delegate()->AllowDefaultTouchActions(top_window))
-    return false;
-
   gfx::Rect hit_bounds_in_screen(display::Screen::GetScreen()
                                      ->GetDisplayNearestWindow(top_window)
                                      .work_area());
@@ -451,14 +421,4 @@ void BackGestureEventHandler::SendBackEvent(const gfx::Point& screen_location) {
                                            BackGestureEndType::kBack));
 }
 
-bool BackGestureEventHandler::ShouldWaitForTouchPressAck(
-    const gfx::Point& screen_location) {
-  if (!CanStartGoingBack(screen_location))
-    return false;
-
-  aura::Window* top_window = window_util::GetTopWindow();
-  return !top_window->GetProperty(kIsShowingInOverviewKey) &&
-         Shell::Get()->shell_delegate()->ShouldWaitForTouchPressAck(top_window);
-}
-
 }  // namespace ash

ash/wm/gestures/back_gesture/back_gesture_event_handler.h

@@ -58,12 +58,6 @@ class BackGestureEventHandler : public display::DisplayObserver,
 
   void SendBackEvent(const gfx::Point& screen_location);
 
-  // Returns true if we should wait for touch press ack to decide whether to
-  // show back gesture. If true, BackGestureEventHandler should not handle touch
-  // press event in OnTouchEvent() but should wait after touch ack has been
-  // received.
-  bool ShouldWaitForTouchPressAck(const gfx::Point& screen_location);
-
   // True if swiping from left edge to go to previous page is in progress.
   bool going_back_started_ = false;
 
@@ -104,13 +98,6 @@ class BackGestureEventHandler : public display::DisplayObserver,
   // instead of going back.
   ui::GestureProviderAura gesture_provider_;
 
-  // False if BackGestureEventHandler should not handle touch events directly in
-  // OnTouchEvent(), but should wait after touch ack is received. This is needed
-  // as the window's touch action (if exist) will only be set after it sees the
-  // touch start event and we'll need the touch action information to decide
-  // whether back gesture should be shown.
-  bool should_wait_for_touch_ack_ = false;
-
   // Start scenario type of the back gesture, used for related metrics.
   BackGestureStartScenarioType back_gesture_start_scenario_type_ =
       BackGestureStartScenarioType::kMaxValue;

chrome/browser/ui/ash/back_gesture_browsertest.cc

-// Copyright 2020 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 "ash/public/cpp/tablet_mode.h"
-#include "ash/public/cpp/test/shell_test_api.h"
-#include "base/path_service.h"
-#include "chrome/browser/ui/browser.h"
-#include "chrome/browser/ui/browser_window.h"
-#include "chrome/browser/ui/tabs/tab_strip_model.h"
-#include "chrome/test/base/in_process_browser_test.h"
-#include "chrome/test/base/ui_test_utils.h"
-#include "content/public/browser/render_widget_host.h"
-#include "content/public/browser/render_widget_host_view.h"
-#include "content/public/browser/web_contents.h"
-#include "content/public/test/browser_test.h"
-#include "content/public/test/browser_test_base.h"
-#include "content/public/test/hit_test_region_observer.h"
-#include "net/dns/mock_host_resolver.h"
-#include "ui/aura/window.h"
-#include "ui/base/test/ui_controls_aura.h"
-#include "ui/events/test/event_generator.h"
-#include "ui/events/types/event_type.h"
-
-namespace {
-
-// The class to record received gesture events and key events to verify if back
-// gesture has been performed.
-class BackGestureEventRecorder : public ui::EventHandler {
- public:
-  BackGestureEventRecorder() = default;
-  BackGestureEventRecorder(const BackGestureEventRecorder&) = delete;
-  BackGestureEventRecorder& operator=(const BackGestureEventRecorder&) = delete;
-  ~BackGestureEventRecorder() override = default;
-
-  // ui::EventHandler:
-  void OnGestureEvent(ui::GestureEvent* event) override {
-    received_event_types_.insert(event->type());
-    if (wait_for_event_ == event->type() && run_loop_) {
-      run_loop_->Quit();
-      wait_for_event_ = ui::EventType::ET_UNKNOWN;
-    }
-  }
-
-  void OnKeyEvent(ui::KeyEvent* event) override {
-    // If back gesture can be performed, a ui::VKEY_BROWSR_BACK key pressed and
-    // key released will be generated.
-    received_event_types_.insert(event->type());
-  }
-
-  void WaitUntilReceivedGestureEvent(ui::EventType event_type) {
-    wait_for_event_ = event_type;
-    run_loop_ = std::make_unique<base::RunLoop>();
-    run_loop_->Run();
-  }
-
-  bool HasReceivedEvent(ui::EventType event_type) {
-    return base::Contains(received_event_types_, event_type);
-  }
-
-  void Reset() {
-    received_event_types_.clear();
-    wait_for_event_ = ui::EventType::ET_UNKNOWN;
-    if (run_loop_)
-      run_loop_->Quit();
-  }
-
- private:
-  // Stores the event types of the received gesture events.
-  base::flat_set<ui::EventType> received_event_types_;
-  ui::EventType wait_for_event_ = ui::EventType::ET_UNKNOWN;
-  std::unique_ptr<base::RunLoop> run_loop_;
-};
-
-}  // namespace
-
-class BackGestureBrowserTest : public InProcessBrowserTest {
- public:
-  BackGestureBrowserTest() = default;
-  BackGestureBrowserTest(const BackGestureBrowserTest&) = delete;
-  BackGestureBrowserTest& operator=(const BackGestureBrowserTest&) = delete;
-  ~BackGestureBrowserTest() override = default;
-
-  void SetUpOnMainThread() override {
-    InProcessBrowserTest::SetUpOnMainThread();
-    host_resolver()->AddRule("*", "127.0.0.1");
-    base::FilePath test_data_dir;
-    ASSERT_TRUE(base::PathService::Get(base::DIR_SOURCE_ROOT, &test_data_dir));
-    embedded_test_server()->ServeFilesFromDirectory(
-        test_data_dir.AppendASCII("chrome/test/data/ash/back_gesture"));
-    ASSERT_TRUE(embedded_test_server()->Start());
-
-    // Enter tablet mode.
-    ash::ShellTestApi().SetTabletModeEnabledForTest(true);
-    ASSERT_TRUE(ash::TabletMode::Get()->InTabletMode());
-  }
-
-  content::RenderWidgetHost* GetRenderWidgetHost() {
-    return browser()
-        ->tab_strip_model()
-        ->GetActiveWebContents()
-        ->GetRenderWidgetHostView()
-        ->GetRenderWidgetHost();
-  }
-};
-
-// Test back gesture behavior with different touch actions.
-IN_PROC_BROWSER_TEST_F(BackGestureBrowserTest, TouchActions) {
-  // Navigate to a page with {touch-action: none} defined.
-  ui_test_utils::NavigateToURL(browser(), embedded_test_server()->GetURL(
-                                              "/page_touch_action_none.html"));
-  content::HitTestRegionObserver observer(
-      GetRenderWidgetHost()->GetFrameSinkId());
-  observer.WaitForHitTestData();
-
-  ASSERT_EQ(browser()->tab_strip_model()->count(), 1);
-
-  aura::Window* browser_window = browser()->window()->GetNativeWindow();
-  const gfx::Rect bounds = browser()->window()->GetBounds();
-  const gfx::Point start_point = bounds.left_center();
-  const gfx::Point end_point =
-      gfx::Point(start_point.x() + 200, start_point.y());
-
-  BackGestureEventRecorder recorder;
-  browser_window->AddPreTargetHandler(&recorder);
-
-  ui::test::EventGenerator event_generator(browser_window->GetRootWindow(),
-                                           browser_window);
-  event_generator.set_current_screen_location(start_point);
-  event_generator.PressTouch();
-  event_generator.MoveTouch(end_point);
-  event_generator.ReleaseTouch();
-  recorder.WaitUntilReceivedGestureEvent(ui::EventType::ET_GESTURE_END);
-
-  // BackGestureEventHandler did not handle gesture scroll events, so |recorder|
-  // should be able to get the scroll events.
-  EXPECT_TRUE(recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_TAP_DOWN));
-  EXPECT_TRUE(
-      recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_SCROLL_BEGIN));
-  EXPECT_TRUE(
-      recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_SCROLL_UPDATE));
-  EXPECT_TRUE(recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_SCROLL_END) ||
-              recorder.HasReceivedEvent(ui::EventType::ET_SCROLL_FLING_START));
-  // ui::VKEY_BROWSR_BACK key pressed and key released will not be generated
-  // because back operation is not performed.
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_KEY_PRESSED));
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_KEY_RELEASED));
-
-  recorder.Reset();
-
-  // Now navigate to a page with {touch-action: auto} defined.
-  ui_test_utils::NavigateToURL(browser(), embedded_test_server()->GetURL(
-                                              "/page_touch_action_auto.html"));
-  content::HitTestRegionObserver observer2(
-      GetRenderWidgetHost()->GetFrameSinkId());
-  observer2.WaitForHitTestData();
-
-  event_generator.set_current_screen_location(start_point);
-  event_generator.PressTouch();
-  event_generator.MoveTouch(end_point);
-  event_generator.ReleaseTouch();
-  recorder.WaitUntilReceivedGestureEvent(ui::EventType::ET_GESTURE_END);
-
-  // BackGestureEventHandler has handled gesture scroll events, so |recorder|
-  // should not be able to get the scroll events.
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_TAP_DOWN));
-  EXPECT_FALSE(
-      recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_SCROLL_BEGIN));
-  EXPECT_FALSE(
-      recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_SCROLL_UPDATE));
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_GESTURE_SCROLL_END));
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_SCROLL_FLING_START));
-  // ui::VKEY_BROWSR_BACK key pressed and key released will be generated because
-  // back operation can be performed.
-  EXPECT_TRUE(recorder.HasReceivedEvent(ui::EventType::ET_KEY_PRESSED));
-  EXPECT_TRUE(recorder.HasReceivedEvent(ui::EventType::ET_KEY_RELEASED));
-  browser_window->RemovePreTargetHandler(&recorder);
-}
-
-// Test the back gesture behavior on page that has prevented default touch
-// behavior.
-IN_PROC_BROWSER_TEST_F(BackGestureBrowserTest, PreventDefault) {
-  ui_test_utils::NavigateToURL(
-      browser(), embedded_test_server()->GetURL("/page_prevent_default.html"));
-  content::HitTestRegionObserver observer(
-      GetRenderWidgetHost()->GetFrameSinkId());
-  observer.WaitForHitTestData();
-
-  ASSERT_EQ(browser()->tab_strip_model()->count(), 1);
-
-  aura::Window* browser_window = browser()->window()->GetNativeWindow();
-  const gfx::Rect bounds = browser()->window()->GetBounds();
-  BackGestureEventRecorder recorder;
-  browser_window->AddPreTargetHandler(&recorder);
-
-  // Start drag on the page that prevents default touch behavior.
-  const gfx::Point start_point = bounds.left_center();
-  const gfx::Point end_point =
-      gfx::Point(start_point.x() + 200, start_point.y());
-  ui::test::EventGenerator event_generator(browser_window->GetRootWindow(),
-                                           browser_window);
-  event_generator.set_current_screen_location(start_point);
-  event_generator.PressTouch();
-  event_generator.MoveTouch(end_point);
-  event_generator.ReleaseTouch();
-  recorder.WaitUntilReceivedGestureEvent(ui::EventType::ET_GESTURE_END);
-
-  // ui::VKEY_BROWSR_BACK key pressed and key released will not be generated
-  // because back operation is not performed.
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_KEY_PRESSED));
-  EXPECT_FALSE(recorder.HasReceivedEvent(ui::EventType::ET_KEY_RELEASED));
-  browser_window->RemovePreTargetHandler(&recorder);
-}

chrome/browser/ui/ash/chrome_shell_delegate.cc

@@ -32,8 +32,6 @@
 #include "chromeos/services/multidevice_setup/multidevice_setup_service.h"
 #include "content/public/browser/device_service.h"
 #include "content/public/browser/media_session_service.h"
-#include "content/public/browser/render_widget_host.h"
-#include "content/public/browser/render_widget_host_view.h"
 #include "ui/aura/window.h"
 #include "url/gurl.h"
 
@@ -42,17 +40,6 @@ namespace {
 const char kKeyboardShortcutHelpPageUrl[] =
     "https://support.google.com/chromebook/answer/183101";
 
-content::WebContents* GetActiveWebContentsForNativeBrowserWindow(
-    gfx::NativeWindow window) {
-  if (!window)
-    return nullptr;
-  BrowserView* browser_view =
-      BrowserView::GetBrowserViewForNativeWindow(window);
-  if (!browser_view)
-    return nullptr;
-  return browser_view->browser()->tab_strip_model()->GetActiveWebContents();
-}
-
 }  // namespace
 
 ChromeShellDelegate::ChromeShellDelegate() = default;
@@ -76,41 +63,15 @@ void ChromeShellDelegate::OpenKeyboardShortcutHelpPage() const {
 }
 
 bool ChromeShellDelegate::CanGoBack(gfx::NativeWindow window) const {
+  BrowserView* browser_view =
+      BrowserView::GetBrowserViewForNativeWindow(window);
+  if (!browser_view)
+    return false;
   content::WebContents* contents =
-      GetActiveWebContentsForNativeBrowserWindow(window);
-  return contents ? contents->GetController().CanGoBack() : false;
-}
-
-bool ChromeShellDelegate::AllowDefaultTouchActions(gfx::NativeWindow window) {
-  content::WebContents* contents =
-      GetActiveWebContentsForNativeBrowserWindow(window);
-  if (!contents)
-    return true;
-  content::RenderWidgetHostView* render_widget_host_view =
-      contents->GetRenderWidgetHostView();
-  if (!render_widget_host_view)
-    return true;
-  content::RenderWidgetHost* render_widget_host =
-      render_widget_host_view->GetRenderWidgetHost();
-  if (!render_widget_host)
-    return true;
-  base::Optional<cc::TouchAction> allowed_touch_action =
-      render_widget_host->GetAllowedTouchAction();
-  return allowed_touch_action.has_value()
-             ? *allowed_touch_action != cc::TouchAction::kNone
-             : true;
-}
-
-bool ChromeShellDelegate::ShouldWaitForTouchPressAck(gfx::NativeWindow window) {
-  content::WebContents* contents =
-      GetActiveWebContentsForNativeBrowserWindow(window);
+      browser_view->browser()->tab_strip_model()->GetActiveWebContents();
   if (!contents)
     return false;
-  content::RenderWidgetHostView* render_widget_host_view =
-      contents->GetRenderWidgetHostView();
-  if (!render_widget_host_view)
-    return false;
-  return !!render_widget_host_view->GetRenderWidgetHost();
+  return contents->GetController().CanGoBack();
 }
 
 bool ChromeShellDelegate::IsTabDrag(const ui::OSExchangeData& drop_data) {

chrome/browser/ui/ash/chrome_shell_delegate.h

@@ -24,8 +24,6 @@ class ChromeShellDelegate : public ash::ShellDelegate {
       ash::BackGestureContextualNudgeController* controller) override;
   void OpenKeyboardShortcutHelpPage() const override;
   bool CanGoBack(gfx::NativeWindow window) const override;
-  bool AllowDefaultTouchActions(gfx::NativeWindow window) override;
-  bool ShouldWaitForTouchPressAck(gfx::NativeWindow window) override;
   bool IsTabDrag(const ui::OSExchangeData& drop_data) override;
   aura::Window* CreateBrowserForTabDrop(
       aura::Window* source_window,

chrome/test/BUILD.gn

@@ -2394,7 +2394,6 @@ if (!is_android) {
         "../browser/ui/app_list/chrome_app_list_model_updater_browsertest.cc",
         "../browser/ui/ash/accelerator_commands_browsertest.cc",
         "../browser/ui/ash/assistant/assistant_context_browsertest.cc",
-        "../browser/ui/ash/back_gesture_browsertest.cc",
         "../browser/ui/ash/chrome_new_window_client_browsertest.cc",
         "../browser/ui/ash/chrome_screenshot_grabber_browsertest.cc",
         "../browser/ui/ash/keyboard/keyboard_controller_browsertest.cc",

chrome/test/data/ash/back_gesture/page_prevent_default.html

-<!DOCTYPE html>
-<html>
-<style>
-body {
-    position: absolute;
-    width: 100%;
-    height: 100%;
-    margin: 0;
-    padding: 0;
-}
-#prevent_default_id {
-    width: 100%;
-    height: 100%;
-}
-</style>
-<body>
-  <div id="prevent_default_id"></div>
-<script>
-document.querySelector("#prevent_default_id").addEventListener(
-    "touchmove", function(e) { e.preventDefault(); });
-</script>
-</body>
-</html>

chrome/test/data/ash/back_gesture/page_touch_action_default.html

-<!DOCTYPE html>
-<html>
-<style>
-body {
-    position: absolute;
-    width: 100%;
-    height: 100%;
-    margin: 0;
-    padding: 0;
-    touch-action: auto;
-}
-</style>
-<body>
-</body>
-</html>

chrome/test/data/ash/back_gesture/page_touch_action_none.html

-<!DOCTYPE html>
-<html>
-<style>
-body {
-    position: absolute;
-    width: 100%;
-    height: 100%;
-    margin: 0;
-    padding: 0;
-    touch-action: none;
-}
-</style>
-<body>
-</body>
-</html>

content/browser/renderer_host/render_widget_host_impl.cc

@@ -1671,10 +1671,6 @@ void RenderWidgetHostImpl::GetScreenInfo(ScreenInfo* result) {
     input_router_->SetDeviceScaleFactor(result->device_scale_factor);
 }
 
-base::Optional<cc::TouchAction> RenderWidgetHostImpl::GetAllowedTouchAction() {
-  return input_router_->AllowedTouchAction();
-}
-
 void RenderWidgetHostImpl::DragTargetDragEnter(
     const DropData& drop_data,
     const gfx::PointF& client_pt,

content/browser/renderer_host/render_widget_host_impl.h

@@ -228,7 +228,6 @@ class CONTENT_EXPORT RenderWidgetHostImpl
   void AddObserver(RenderWidgetHostObserver* observer) override;
   void RemoveObserver(RenderWidgetHostObserver* observer) override;
   void GetScreenInfo(content::ScreenInfo* result) override;
-  base::Optional<cc::TouchAction> GetAllowedTouchAction() override;
   // |drop_data| must have been filtered. The embedder should call
   // FilterDropData before passing the drop data to RWHI.
   void DragTargetDragEnter(const DropData& drop_data,

content/public/browser/render_widget_host.h

@@ -12,7 +12,6 @@
 
 #include "base/callback.h"
 #include "base/i18n/rtl.h"
-#include "base/optional.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/native_web_keyboard_event.h"
@@ -31,10 +30,6 @@ class WebMouseEvent;
 class WebMouseWheelEvent;
 }
 
-namespace cc {
-enum class TouchAction;
-}
-
 namespace gfx {
 class Point;
 }
@@ -283,9 +278,6 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Sender {
   // Get the screen info corresponding to this render widget.
   virtual void GetScreenInfo(ScreenInfo* result) = 0;
 
-  // Get the allowed touch action corresponding to this render widget.
-  virtual base::Optional<cc::TouchAction> GetAllowedTouchAction() = 0;
-
   // Drag-and-drop drop target messages that get sent to Blink.
   virtual void DragTargetDragEnter(
       const DropData& drop_data,