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

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

Index: chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java b/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
index 61164ab434b43ec87f4695ee7747a9ce85f940bc..31caa2e0f473b527095309872c0f045ac11d6346 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
@@ -857,13 +857,13 @@ public class PaymentRequestImpl implements PaymentRequest, PaymentRequestUI.Clie
                 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());
     }