Add feature flag for fullscreen alert bubble.

This CL add a feature flag kFullscreenAlertBubble to the feature
of Fullscreen Alert Bubble.

Bug: 1107185
Change-Id: I76c3ef33df6056f7a33f0a23294ce2ef169a2326
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2520323Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Xiaodan Zhu <zxdan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824911}

ash/public/cpp/ash_features.cc

@@ -120,6 +120,9 @@ const base::Feature kHideShelfControlsInTabletMode{
 const base::Feature kReverseScrollGestures{"EnableReverseScrollGestures",
                                            base::FEATURE_ENABLED_BY_DEFAULT};
 
+const base::Feature kFullscreenAlertBubble{"EnableFullscreenBubble",
+                                           base::FEATURE_ENABLED_BY_DEFAULT};
+
 const base::Feature kSystemTrayMicGainSetting{"SystemTrayMicGainSetting",
                                               base::FEATURE_ENABLED_BY_DEFAULT};
 
@@ -255,6 +258,10 @@ bool IsReverseScrollGesturesEnabled() {
   return base::FeatureList::IsEnabled(kReverseScrollGestures);
 }
 
+bool IsFullscreenAlertBubbleEnabled() {
+  return base::FeatureList::IsEnabled(kFullscreenAlertBubble);
+}
+
 bool AreContextualNudgesEnabled() {
   if (!IsHideShelfControlsInTabletModeEnabled())
     return false;

ash/public/cpp/ash_features.h

@@ -159,6 +159,12 @@ ASH_PUBLIC_EXPORT extern const base::Feature kHideShelfControlsInTabletMode;
 // TODO(https://crbug.com/1107183): Remove this after the feature is launched.
 ASH_PUBLIC_EXPORT extern const base::Feature kReverseScrollGestures;
 
+// When enabled, there will be an alert bubble showing up when the device
+// returns from low brightness (e.g., sleep, closed cover) without a lock screen
+// and the active window is in fullscreen.
+// TODO(https://crbug.com/1107185): Remove this after the feature is launched.
+ASH_PUBLIC_EXPORT extern const base::Feature kFullscreenAlertBubble;
+
 // Enables sliders for setting mic gain levels in the more audio settings
 // section in the system tray.
 ASH_PUBLIC_EXPORT extern const base::Feature kSystemTrayMicGainSetting;
@@ -234,6 +240,8 @@ ASH_PUBLIC_EXPORT bool IsHideShelfControlsInTabletModeEnabled();
 
 ASH_PUBLIC_EXPORT bool IsReverseScrollGesturesEnabled();
 
+ASH_PUBLIC_EXPORT bool IsFullscreenAlertBubbleEnabled();
+
 ASH_PUBLIC_EXPORT bool AreContextualNudgesEnabled();
 
 ASH_PUBLIC_EXPORT bool IsSystemTrayMicGainSettingEnabled();

ash/session/fullscreen_controller.cc

@@ -7,6 +7,7 @@
 #include <limits>
 
 #include "ash/login/ui/lock_screen.h"
+#include "ash/public/cpp/ash_features.h"
 #include "ash/session/fullscreen_alert_bubble.h"
 #include "ash/session/session_controller_impl.h"
 #include "ash/shelf/shelf.h"
@@ -56,6 +57,9 @@ void FullscreenController::MaybeExitFullscreen() {
 }
 
 void FullscreenController::MaybeShowAlert() {
+  if (!features::IsFullscreenAlertBubbleEnabled())
+    return;
+
   // 1. Check if there is a lock/login screen showing up.
   if (LockScreen::HasInstance())
     return;