back_gesture: Allowing go back in overview mode.

Bug: 1002733
Change-Id: I5fb541119dc56f98b70358fc68b70b5fe110a43b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1888102Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711315}

ash/wm/overview/overview_session_unittest.cc

@@ -3132,9 +3132,15 @@ TEST_P(OverviewSessionNewLayoutTest, CheckOverviewItemScrollingBounds) {
   // see if the item moved at all.
   OverviewItem* leftmost_window = GetOverviewItemForWindow(windows[0].get());
 
-  GenerateScrollSequence(gfx::Point(0, 50), gfx::Point(5000, 50));
+  GenerateScrollSequence(
+      gfx::Point(ToplevelWindowEventHandler::kStartGoingBackLeftEdgeInset + 5,
+                 50),
+      gfx::Point(5000, 50));
   const gfx::RectF left_bounds = leftmost_window->target_bounds();
-  GenerateScrollSequence(gfx::Point(0, 50), gfx::Point(5000, 50));
+  GenerateScrollSequence(
+      gfx::Point(ToplevelWindowEventHandler::kStartGoingBackLeftEdgeInset + 5,
+                 50),
+      gfx::Point(5000, 50));
   EXPECT_EQ(left_bounds, leftmost_window->target_bounds());
 
   // Scroll an extreme amount to see if windows on the far right are still in

ash/wm/toplevel_window_event_handler.cc

@@ -45,10 +45,6 @@ namespace {
 // window from the top of the screen in tablet mode.
 constexpr int kDragStartTopEdgeInset = 8;
 
-// How many dips are reserved for gesture events to start swiping to previous
-// page from the left edge of the screen in tablet mode.
-constexpr int kStartGoingBackLeftEdgeInset = 16;
-
 // Returns whether |window| can be moved via a two finger drag given
 // the hittest results of the two fingers.
 bool CanStartTwoFingerMove(aura::Window* window,
@@ -122,14 +118,6 @@ bool CanStartGoingBack(aura::Window* target) {
     return false;
   }
 
-  // Do not enable back gesture while overview mode is active but splitview is
-  // not active.
-  if (shell->overview_controller()->InOverviewSession() &&
-      !SplitViewController::Get(Shell::GetPrimaryRootWindow())
-           ->InSplitViewMode()) {
-    return false;
-  }
-
   // Do not enable back gesture if home screen is visible but not in
   // |kFullscreenSearch| state.
   if (shell->home_screen_controller()->IsHomeScreenVisible() &&
@@ -167,7 +155,8 @@ bool StartedAwayFromLeftArea(ui::GestureEvent* event) {
           .work_area();
 
   gfx::Rect hit_bounds_in_screen(work_area_bounds);
-  hit_bounds_in_screen.set_width(kStartGoingBackLeftEdgeInset);
+  hit_bounds_in_screen.set_width(
+      ToplevelWindowEventHandler::kStartGoingBackLeftEdgeInset);
   return hit_bounds_in_screen.Contains(location_in_screen);
 }
 

ash/wm/toplevel_window_event_handler.h

@@ -51,6 +51,10 @@ class ASH_EXPORT ToplevelWindowEventHandler
   // previous page.
   static constexpr int kFlingVelocityForGoingBack = 1000;
 
+  // How many dips are reserved for gesture events to start swiping to previous
+  // page from the left edge of the screen in tablet mode.
+  static constexpr int kStartGoingBackLeftEdgeInset = 16;
+
   // Describes what triggered ending the drag.
   enum class DragResult {
     // The drag successfully completed.

ash/wm/toplevel_window_event_handler_unittest.cc

@@ -1127,6 +1127,21 @@ TEST_F(ToplevelWindowEventHandlerBackGestureTest, FlingFromLeftEdgeToGoBack) {
   EXPECT_EQ(1, target_back_release.accelerator_count());
 }
 
+TEST_F(ToplevelWindowEventHandlerBackGestureTest, GoBackInOverviewMode) {
+  ui::TestAcceleratorTarget target_back_press, target_back_release;
+  RegisterBackPressAndRelease(&target_back_press, &target_back_release);
+
+  auto* shell = Shell::Get();
+  shell->overview_controller()->StartOverview();
+  ASSERT_TRUE(shell->overview_controller()->InOverviewSession());
+  GetEventGenerator()->GestureScrollSequence(
+      gfx::Point(0, 100),
+      gfx::Point(ToplevelWindowEventHandler::kSwipingDistanceForGoingBack + 10,
+                 100),
+      base::TimeDelta::FromMilliseconds(100), 3);
+  EXPECT_EQ(1, target_back_release.accelerator_count());
+}
+
 TEST_F(ToplevelWindowEventHandlerBackGestureTest, DonotStartGoingBack) {
   ui::TestAcceleratorTarget target_back_press, target_back_release;
   RegisterBackPressAndRelease(&target_back_press, &target_back_release);
@@ -1148,27 +1163,10 @@ TEST_F(ToplevelWindowEventHandlerBackGestureTest, DonotStartGoingBack) {
   EXPECT_EQ(0, target_back_press.accelerator_count());
   EXPECT_EQ(0, target_back_release.accelerator_count());
 
-  // Should not go back while in overview mode but splitview is not active.
-  ASSERT_FALSE(SplitViewController::Get(Shell::GetPrimaryRootWindow())
-                   ->InSplitViewMode());
-  GetSessionControllerClient()->SetSessionState(
-      session_manager::SessionState::ACTIVE);
-  ASSERT_EQ(session_manager::SessionState::ACTIVE,
-            shell->session_controller()->GetSessionState());
-  shell->overview_controller()->StartOverview();
-  ASSERT_TRUE(shell->overview_controller()->InOverviewSession());
-  generator->GestureScrollSequence(
-      start,
-      gfx::Point(ToplevelWindowEventHandler::kSwipingDistanceForGoingBack + 10,
-                 100),
-      base::TimeDelta::FromMilliseconds(100), 3);
-  EXPECT_EQ(0, target_back_press.accelerator_count());
-  EXPECT_EQ(0, target_back_release.accelerator_count());
-
   // Should not go back if home screen is visible and in |kFullscreenAllApps|
   // state.
-  shell->overview_controller()->EndOverview();
-  ASSERT_FALSE(shell->overview_controller()->InOverviewSession());
+  GetSessionControllerClient()->SetSessionState(
+      session_manager::SessionState::ACTIVE);
   shell->home_screen_controller()->GoHome(GetPrimaryDisplay().id());
   ASSERT_TRUE(shell->home_screen_controller()->IsHomeScreenVisible());
   GetAppListTestHelper()->CheckState(AppListViewState::kFullscreenAllApps);