Fix chrome crash issue when payment modifiers are enabled on android.

chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java

 // Copyright 2016 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.payments;
 
 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.graphics.Bitmap;
@@ skipping 839 matching lines @@
 
         PaymentDetailsModifier modifier = getModifier(instrument);
         PaymentItem total = modifier == null ? null : modifier.total;
         if (total == null) total = mRawTotal;
 
         CurrencyFormatter formatter = getOrCreateCurrencyFormatter(total.amount);
         mUiShoppingCart.setTotal(new LineItem(total.label, formatter.getFormattedCurrencyCode(),
                 formatter.format(total.amount.value), false /* isPending */));
         mUiShoppingCart.setAdditionalContents(
                 modifier == null ? null : getLineItems(modifier.additionalDisplayItems));
-        mUI.updateOrderSummarySection(mUiShoppingCart);

[gogerald1, 2017/05/11 20:11:20]

why is this redundant? we have to update UI if mUiShoppingCart is changed, and
this change might happened after UI is shown, so you can do "if (mUI != null)
mUI.update....."

[wuandy1, 2017/05/12 01:34:28]

what i meant was it looked like at the end of updateWith(), mUI is updated with
new shopping cart eventually.

But i think even it's true, it's good to update here anyways, just in case, so
made the change as you suggested.

[gogerald1, 2017/05/12 14:23:04]

This is also called when selected payment option is changed. We should be able
to remove mUI.updateOrderSummarySection from updateWith after
WEB_PAYMENTS_MODIFIERS is removed

     }
 
     /** @return The first modifier that matches the given instrument, or null. */
     @Nullable private PaymentDetailsModifier getModifier(@Nullable PaymentInstrument instrument) {
         if (mModifiers == null || instrument == null) return null;
-        Set<String> methodNames = instrument.getInstrumentMethodNames();
+        // make a copy to ensure it is modifiable.
+        Set<String> methodNames = new HashSet<>(instrument.getInstrumentMethodNames());
         methodNames.retainAll(mModifiers.keySet());
         return methodNames.isEmpty() ? null : mModifiers.get(methodNames.iterator().next());
     }
 
     /**
      * Converts a list of payment items and returns their parsed representation.
      *
      * @param items     The payment items to parse. Can be null.
      * @return A list of valid line items.
      */
@@ skipping 993 matching lines @@
 
     /**
      * The frecency score is calculated according to use count and last use date. The formula is
      * the same as the one used in GetFrecencyScore in autofill_data_model.cc.
      */
     private static final double getFrecencyScore(int count, long date) {
         long currentTime = System.currentTimeMillis();
         return -Math.log((currentTime - date) / (24 * 60 * 60 * 1000) + 2) / Math.log(count + 2);
     }
 }