android: Fix selection popup flicker

In r728805, SelectionPopupControllerImpl post task was converged from
View to Handler. However one of the removeCallbacks calls was
accidentally not converted, which means the task to dismiss the pop up
was never removed as expected sometimes, causing a flicker.

Fixed: 1040457
Change-Id: Iad16cc958b4adce599255de7596b2cbec568154a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994007
Commit-Queue: Bo <boliu@chromium.org>
Commit-Queue: Shimi Zhang <ctzsm@chromium.org>
Auto-Submit: Bo <boliu@chromium.org>
Reviewed-by: Shimi Zhang <ctzsm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729970}

content/public/android/java/src/org/chromium/content/browser/selection/SelectionPopupControllerImpl.java

@@ -553,7 +553,7 @@ public class SelectionPopupControllerImpl extends ActionModeCallbackHelper
     @Override
     public void finishActionMode() {
         mHidden = false;
-        if (mView != null) mView.removeCallbacks(mRepeatingHideRunnable);
+        mHandler.removeCallbacks(mRepeatingHideRunnable);
 
         if (isActionModeValid()) {
             mActionMode.finish();