Make ContentCapture calls directly from the UI thread.

Most calls are bufffered anyways, so by not using a handler we save time spent
on getting a pooled lambda and posting to the the handler.

The only "expensive" operation is flushing, but it makes a oneway binder call
so it might be fine (and if necessary, we can optimize it later).

Bug: 123307965
Test: atest CtsContentCaptureServiceTestCases
Change-Id: I7182c8e193f58fa000396fdb3003e771214bf79b
diff --git a/core/java/android/os/Handler.java b/core/java/android/os/Handler.java
index e8704af..e6c12c7 100644
--- a/core/java/android/os/Handler.java
+++ b/core/java/android/os/Handler.java
@@ -469,6 +469,11 @@
         return sendMessageDelayed(getPostMessage(r), delayMillis);
     }
     
+    /** @hide */
+    public final boolean postDelayed(Runnable r, int what, long delayMillis) {
+        return sendMessageDelayed(getPostMessage(r).setWhat(what), delayMillis);
+    }
+
     /**
      * Causes the Runnable r to be added to the message queue, to be run
      * after the specified amount of time elapses.