Update shelf offset earlier when in gesture nav

- Provide a hint to Launcher to indicate it will be resumed when
  swiping home, which allows us to notify sysui before any potential
  pip invocation, reducing the likelyhood of two conflicting animations
  when entering pip

Bug: 156637223
Change-Id: Iae773e1aac88bbea6f74e1d1332417b448126471

quickstep/src/com/android/launcher3/BaseQuickstepLauncher.java

@@ -304,4 +304,8 @@ public abstract class BaseQuickstepLauncher extends Launcher
     public ShelfPeekAnim getShelfPeekAnim() {
         return mShelfPeekAnim;
     }
+
+    public void setHintUserWillBeActive() {
+        addActivityFlags(ACTIVITY_STATE_USER_WILL_BE_ACTIVE);
+    }
 }