Add aconfig: enable_pip_ui_state_on_entering

This CL adds a new flag into multitask.aconfig, when it's enabled, there
will be an extra callback to Activity#onPictureInPictureUiStateChanged
when system is putting the Activity into PiP mode.

Bug: 303718131
Flag: ENABLE_PIP_UI_STATE_ON_ENTERING
Test: N/A
Change-Id: I4997accbf58208ec50b26b21ecd0fef996b5813a
diff --git a/libs/WindowManager/Shell/aconfig/multitasking.aconfig b/libs/WindowManager/Shell/aconfig/multitasking.aconfig
index 29bdd5c..c366ccd 100644
--- a/libs/WindowManager/Shell/aconfig/multitasking.aconfig
+++ b/libs/WindowManager/Shell/aconfig/multitasking.aconfig
@@ -35,3 +35,10 @@
     description: "Enables taskbar / navbar unification"
     bug: "309671494"
 }
+
+flag {
+    name: "enable_pip_ui_state_on_entering"
+    namespace: "multitasking"
+    description: "Enables PiP UI state callback on entering"
+    bug: "303718131"
+}