[CrOS] Fix left icon transition of password login screen

Bug: 1003885
Change-Id: Iaaf0d34234e7b922e5e68be4e8c35d19aa4deb47
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2622174
Commit-Queue: Thomas Tellier <tellier@google.com>
Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842170}

ash/login/ui/login_password_view.cc

@@ -941,14 +941,22 @@ void LoginPasswordView::HandleLeftIconsVisibilities(bool handling_capslock) {
   }
 
   if (handled_should_show) {
+    // If the view that is currently handled should be shown, we immediately
+    // show it; if the other view should be shown as well, we make it invisible
+    // for the moment and start a cyclic animation that will show these two
+    // views alternatively.
     handled_view->SetVisible(true);
     if (other_should_show) {
       other_view->SetVisible(false);
       left_icon_->ScheduleAnimation(handled_view, other_view);
     }
   } else {
+    // If the view that is currently handled should now be invisible, we
+    // immediately hide it and we abort the cyclic animation if it was running.
+    // We also make the other view visible if needed, as its current state
+    // may depend on how long the animation has been running.
     left_icon_->AbortAnimationIfAny();
-    other_view->SetVisible(should_show_easy_unlock_);
+    other_view->SetVisible(other_should_show);
     handled_view->SetVisible(false);
   }
   password_row_->Layout();

ash/login/ui/login_password_view_test.cc

@@ -356,6 +356,12 @@ TEST_F(LoginPasswordViewTest, SwitchBetweenEasyUnlockAndCapsLock) {
                            base::string16() /*accessibility_label*/);
   EXPECT_TRUE(test_api.easy_unlock_icon()->GetVisible());
   EXPECT_FALSE(test_api.capslock_icon()->GetVisible());
+
+  // Hide the easy unlock icon, the capslock icon should be shown.
+  view_->SetEasyUnlockIcon(EasyUnlockIconId::NONE,
+                           base::string16() /*accessibility_label*/);
+  EXPECT_FALSE(test_api.easy_unlock_icon()->GetVisible());
+  EXPECT_TRUE(test_api.capslock_icon()->GetVisible());
 }
 
 // Verifies that the password textfield clears after a delay when the display