applist: Fix flinging mechanics on shelf and applist.

Previously the fling in the wrong direction would do the same as a fling
in the right direction. (ex. flinging down when dragging up from the
shelf would show the home launcher as well)

Test: ash_unittests HomeLauncherModeGestureHandlerTest.Fling*
Bug: 896510
Change-Id: I0a366eaab679e5e041947a07e80bd82ab495a8af
Reviewed-on: https://chromium-review.googlesource.com/c/1289073
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600860}

ash/app_list/home_launcher_gesture_handler.cc

@@ -571,8 +571,15 @@ bool HomeLauncherGestureHandler::IsFinalStateShow() {
   // If fling velocity is greater than the threshold, show the launcher if
   // sliding up, or hide the launcher if sliding down, irregardless of
   // |last_event_location_|.
-  if (std::fabs(last_scroll_y_) > kScrollVelocityThreshold)
-    return mode_ == Mode::kSlideUpToShow;
+  if (mode_ == Mode::kSlideUpToShow &&
+      last_scroll_y_ < -kScrollVelocityThreshold) {
+    return true;
+  }
+
+  if (mode_ == Mode::kSlideDownToHide &&
+      last_scroll_y_ > kScrollVelocityThreshold) {
+    return false;
+  }
 
   return last_event_location_
              ? IsLastEventInTopHalf(*last_event_location_, display_.work_area())

ash/app_list/home_launcher_gesture_handler_unittest.cc

@@ -138,6 +138,14 @@ TEST_F(HomeLauncherGestureHandlerTest, FlingingSlideUp) {
   auto window = CreateWindowForTesting();
   ASSERT_TRUE(window->IsVisible());
 
+  // Tests that flinging down in this mode will keep the window visible.
+  DoPress(Mode::kSlideUpToShow);
+  GetGestureHandler()->OnScrollEvent(gfx::Point(0, 300), 10.f);
+  GetGestureHandler()->OnReleaseEvent(gfx::Point(0, 300), nullptr);
+  ASSERT_TRUE(window->IsVisible());
+
+  // Tests that flinging up in this mode will hide the window and show the
+  // home launcher.
   DoPress(Mode::kSlideUpToShow);
   GetGestureHandler()->OnScrollEvent(gfx::Point(0, 300), -10.f);
   GetGestureHandler()->OnReleaseEvent(gfx::Point(0, 300), nullptr);
@@ -153,6 +161,13 @@ TEST_F(HomeLauncherGestureHandlerTest, FlingingSlideDown) {
   wm::GetWindowState(window.get())->Minimize();
   ASSERT_FALSE(window->IsVisible());
 
+  // Tests that flinging up in this mode will not show the mru window.
+  DoPress(Mode::kSlideDownToHide);
+  GetGestureHandler()->OnScrollEvent(gfx::Point(0, 100), -10.f);
+  GetGestureHandler()->OnReleaseEvent(gfx::Point(0, 100), nullptr);
+  ASSERT_FALSE(window->IsVisible());
+
+  // Tests that flinging down in this mode will show the mru window.
   DoPress(Mode::kSlideDownToHide);
   GetGestureHandler()->OnScrollEvent(gfx::Point(0, 100), 10.f);
   GetGestureHandler()->OnReleaseEvent(gfx::Point(0, 100), nullptr);