Run pending-intent-sent callback on UI thread.

Before this CL the callback passed to
StatusBar.startPendingIntentDismissingKeyguard() was being run on a
background thread otherwise used to run the pending intent. This is not
obvious to the caller of startPendingIntentDismissingKeyguard(), so with
this CL we call the callback to the UI thread and make it clear that's
the case.

Bug: 120894295
Test: atest SystemUITests
Test: manual - ensure HUN is removed when pressing HUN smart action.
Change-Id: If106b697527843dd74e37d14de882d5f08187285
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/policy/SmartReplyView.java b/packages/SystemUI/src/com/android/systemui/statusbar/policy/SmartReplyView.java
index 4fa8321..f85d803 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/policy/SmartReplyView.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/policy/SmartReplyView.java
@@ -16,8 +16,6 @@
 import android.graphics.drawable.InsetDrawable;
 import android.graphics.drawable.RippleDrawable;
 import android.os.Bundle;
-import android.os.Handler;
-import android.os.Looper;
 import android.text.Layout;
 import android.text.TextPaint;
 import android.text.method.TransformationMethod;
@@ -65,7 +63,6 @@
     private final SmartReplyConstants mConstants;
     private final KeyguardDismissUtil mKeyguardDismissUtil;
     private final NotificationRemoteInputManager mRemoteInputManager;
-    private final Handler mMainThreadHandler = new Handler(Looper.getMainLooper());
 
     /**
      * The upper bound for the height of this view in pixels. Notifications are automatically
@@ -311,8 +308,7 @@
                         () -> {
                             smartReplyController.smartActionClicked(
                                     entry, actionIndex, action, smartActions.fromAssistant);
-                            postOnUiThread(() ->
-                                    headsUpManager.removeNotification(entry.key, true));
+                            headsUpManager.removeNotification(entry.key, true);
                         }));
 
         // TODO(b/119010281): handle accessibility
@@ -323,10 +319,6 @@
         return button;
     }
 
-    private void postOnUiThread(Runnable runnable) {
-        mMainThreadHandler.post(runnable);
-    }
-
     @Override
     public LayoutParams generateLayoutParams(AttributeSet attrs) {
         return new LayoutParams(mContext, attrs);