Add HomeTransitionListener to launcher.

Fixes: 279514548
Bug: 284474103
Bug: 306053414

Flag: LEGACY ENABLE_HOME_TRANSITION_LISTENER DISABLED
Test: App launch -> Hotseat -> Taskbar stashes
      Transluscent app launch and launcher still visible -> No change
      Going home -> Hotseat visible

Change-Id: I6db5253ada3e3b37dfae124f3ee88a9805804fb8
diff --git a/src/com/android/launcher3/config/FeatureFlags.java b/src/com/android/launcher3/config/FeatureFlags.java
index 2ca8a1e..713009e 100644
--- a/src/com/android/launcher3/config/FeatureFlags.java
+++ b/src/com/android/launcher3/config/FeatureFlags.java
@@ -308,6 +308,10 @@
             "ENABLE_DYNAMIC_TASKBAR_THRESHOLDS", ENABLED,
             "Enables taskbar thresholds that scale based on screen size.");
 
+    public static final BooleanFlag ENABLE_HOME_TRANSITION_LISTENER = getDebugFlag(306053414,
+            "ENABLE_HOME_TRANSITION_LISTENER", DISABLED,
+            "Enables launcher to listen to all transitions that include home activity.");
+
     // TODO(Block 21): Clean up flags
     public static final BooleanFlag ENABLE_APP_ICON_FOR_INLINE_SHORTCUTS = getDebugFlag(270395087,
             "ENABLE_APP_ICON_IN_INLINE_SHORTCUTS", DISABLED, "Show app icon for inline shortcut");