Reset need_trigger_scrollbar_show_ in SAC::DidMouseLeave

cc/input/scrollbar_animation_controller_unittest.cc

Index: cc/input/scrollbar_animation_controller_unittest.cc
diff --git a/cc/input/scrollbar_animation_controller_unittest.cc b/cc/input/scrollbar_animation_controller_unittest.cc
index 3d0855e65e1adeedc1842b264b4b39454ce6c77e..a8152a4158ca86cc5a66cd93390323a09ef810f7 100644
--- a/cc/input/scrollbar_animation_controller_unittest.cc
+++ b/cc/input/scrollbar_animation_controller_unittest.cc
@@ -1044,7 +1044,7 @@ TEST_F(ScrollbarAnimationControllerAuraOverlayTest,
 // Scrollbars should cancel delay show when mouse hover hidden scrollbar then
 // move out of window.
 TEST_F(ScrollbarAnimationControllerAuraOverlayTest,
-       MouseHoverThenLeaveShouldCancelShow) {
+       MouseHoverThenLeaveShouldCancelShowThenEnterShouldShow) {
   base::TimeTicks time;
   time += base::TimeDelta::FromSeconds(1);
 
@@ -1060,6 +1060,19 @@ TEST_F(ScrollbarAnimationControllerAuraOverlayTest,
   scrollbar_controller_->DidMouseLeave();
   EXPECT_TRUE(client_.start_fade().is_null() ||
               client_.start_fade().IsCancelled());
+
+  // Move mouse over scrollbar.
+  scrollbar_controller_->DidMouseMoveNear(VERTICAL, 0);
+
+  // An show animation should have been enqueued.
+  EXPECT_FALSE(client_.start_fade().is_null());
+  EXPECT_FALSE(client_.start_fade().IsCancelled());
+  EXPECT_EQ(kShowDelay, client_.delay());
+
+  // Play the delay animation.
+  client_.start_fade().Run();
+  EXPECT_TRUE(client_.start_fade().IsCancelled());
+  EXPECT_FALSE(scrollbar_controller_->ScrollbarsHidden());
 }
 
 class ScrollbarAnimationControllerAndroidTest