Add synchronous transaction to wait for setInputWindow to complete (2/n)

Added InputWindowCommand syncInputWindows

This will allow the client to request SF to wait until setInputWindow
has completed on the InputDispatcher side.

Bug: 123041491
Test: Builds, no execution yet
Change-Id: Ibb5539455d20e4d612696ae7164ce84130bf91b4
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index a4f6005..6d1c9fc 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -4180,6 +4180,10 @@
         flags |= eTraversalNeeded;
     }
 
+    if (inputWindowCommands.syncInputWindows) {
+        flags |= eTraversalNeeded;
+    }
+
     mPendingInputWindowCommands.merge(inputWindowCommands);
     return flags;
 }