Add haptic effect for the seekbar in Settings 3/n.

- in Pointer speed, perform haptic feedback as the seekbar's progress value is updated.
- screenshot, https://screenshot.googleplex.com/997TwHNc4TJtsG7

Bug: 174109628
Test: make -j42 RunSettingsRoboTests ROBOTEST_FILTER=PointerSpeedPreferenceTest
Change-Id: I385f290ae8ca39944eaeb054298db45da6acab4c

src/com/android/settings/PointerSpeedPreference.java

@@ -16,6 +16,8 @@
 
 package com.android.settings;
 
+import static android.view.HapticFeedbackConstants.CLOCK_TICK;
+
 import android.content.ContentResolver;
 import android.content.Context;
 import android.database.ContentObserver;
@@ -37,6 +39,7 @@ public class PointerSpeedPreference extends SeekBarDialogPreference implements
     private boolean mRestoredOldState;
 
     private boolean mTouchInProgress;
+    private int mLastProgress = -1;
 
     private ContentObserver mSpeedObserver = new ContentObserver(new Handler()) {
         @Override
@@ -76,6 +79,10 @@ public class PointerSpeedPreference extends SeekBarDialogPreference implements
         if (!mTouchInProgress) {
             mIm.tryPointerSpeed(progress + InputManager.MIN_POINTER_SPEED);
         }
+        if (progress != mLastProgress) {
+            seekBar.performHapticFeedback(CLOCK_TICK);
+            mLastProgress = progress;
+        }
     }
 
     public void onStartTrackingTouch(SeekBar seekBar) {