added rounded corners & created file for rounded corners

chrome/android/java/src/org/chromium/chrome/browser/contextmenu/TabularContextMenuUi.java

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.contextmenu;
 
 import android.app.Activity;
 import android.app.Dialog;
 import android.content.DialogInterface;
 import android.content.res.Resources;
@@ skipping 37 matching lines @@
     public TabularContextMenuUi(Runnable onShareItemClicked) {
         mOnShareItemClicked = onShareItemClicked;
     }
 
     @Override
     public void displayMenu(Activity activity, ContextMenuParams params,
             List<Pair<Integer, List<ContextMenuItem>>> items, Callback<Integer> onItemClicked,
             final Runnable onMenuShown, final Runnable onMenuClosed) {
         mCallback = onItemClicked;
         mDialog = createDialog(activity, params, items);
+
         mDialog.getWindow().setBackgroundDrawable(ApiCompatibilityUtils.getDrawable(
-                activity.getResources(), R.drawable.bg_find_toolbar_popup));
+                activity.getResources(), R.drawable.white_with_rounded_corners));
 
         mDialog.setOnShowListener(new DialogInterface.OnShowListener() {
             @Override
             public void onShow(DialogInterface dialogInterface) {
                 onMenuShown.run();
             }
         });
 
         mDialog.setOnDismissListener(new DialogInterface.OnDismissListener() {
             @Override
@@ skipping 167 matching lines @@
                             activity, params, itemGroup.second, isImageTab, maxCount)));
         }
         TabularContextMenuViewPager pager =
                 (TabularContextMenuViewPager) view.findViewById(R.id.custom_pager);
         pager.setAdapter(new TabularContextMenuPagerAdapter(viewGroups));
 
         TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
         if (itemGroups.size() <= 1) {
             tabLayout.setVisibility(View.GONE);
         }
+
         tabLayout.setupWithViewPager((ViewPager) view.findViewById(R.id.custom_pager));
 
         return view;
     }
 
     /**
      * When an thumbnail is retrieved for the header of an image, this will set the header to
      * that particular bitmap.
      */
     public void onImageThumbnailRetrieved(Bitmap bitmap) {
         if (mHeaderImageView != null) {
             mHeaderImageView.setImageBitmap(bitmap);
         }
     }
 
     @Override
     public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
         mDialog.dismiss();
         mCallback.onResult((int) id);
     }
 }