[1/n] Add WALLPAPER_PICKER_GRID_APPLY_BUTTON to SysUi Flags.kt

Resubmit of ag/24343660 that was reverted due to failure to merge on main.

Test: N/A
Bug: 294866904
Change-Id: Ibd45b0039959d24308a47bde4652ec768e7d9ceb
diff --git a/packages/SystemUI/customization/src/com/android/systemui/shared/customization/data/content/CustomizationProviderContract.kt b/packages/SystemUI/customization/src/com/android/systemui/shared/customization/data/content/CustomizationProviderContract.kt
index 46f5971..92d2bd2 100644
--- a/packages/SystemUI/customization/src/com/android/systemui/shared/customization/data/content/CustomizationProviderContract.kt
+++ b/packages/SystemUI/customization/src/com/android/systemui/shared/customization/data/content/CustomizationProviderContract.kt
@@ -190,6 +190,9 @@
         /** Flag denoting transit clock are enabled in wallpaper picker. */
         const val FLAG_NAME_PAGE_TRANSITIONS = "wallpaper_picker_page_transitions"
 
+        /** Flag denoting adding apply button to wallpaper picker's grid preview page. */
+        const val FLAG_NAME_GRID_APPLY_BUTTON = "wallpaper_picker_grid_apply_button"
+
         /** Flag denoting whether preview loading animation is enabled. */
         const val FLAG_NAME_WALLPAPER_PICKER_PREVIEW_ANIMATION =
             "wallpaper_picker_preview_animation"
diff --git a/packages/SystemUI/src/com/android/systemui/flags/Flags.kt b/packages/SystemUI/src/com/android/systemui/flags/Flags.kt
index 0e2e0c5..35a5d61 100644
--- a/packages/SystemUI/src/com/android/systemui/flags/Flags.kt
+++ b/packages/SystemUI/src/com/android/systemui/flags/Flags.kt
@@ -226,6 +226,12 @@
     val WALLPAPER_PICKER_PAGE_TRANSITIONS =
         unreleasedFlag("wallpaper_picker_page_transitions")
 
+    /** Add "Apply" button to wall paper picker's grid preview page. */
+    // TODO(b/294866904): Tracking bug.
+    @JvmField
+    val WALLPAPER_PICKER_GRID_APPLY_BUTTON =
+            unreleasedFlag("wallpaper_picker_grid_apply_button")
+
     /** Whether to run the new udfps keyguard refactor code. */
     // TODO(b/279440316): Tracking bug.
     @JvmField