We want to prevent the merchant website from finding the exact amount of money in your wallet. 

Comparing total to wallet balance was the original intention, but we don't think that's a strong enough use case. In addition, the payment app is free to ask user for refill their balance or do so automatically.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b739440826fb34eaed9931838845e3adc32727ac

commit b739440826fb34eaed9931838845e3adc32727ac
Author: gogerald <gogerald@google.com>
Date: Fri Jul 21 17:47:25 2017

[Payments] Remove "total" from IS_READY_TO_PAY

Bug:  740257 
Change-Id: Ib4b52311d30a663695f18ca6140b74531cb0d583
Reviewed-on: https://chromium-review.googlesource.com/581734
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488700}
[modify] https://crrev.com/b739440826fb34eaed9931838845e3adc32727ac/chrome/android/java/src/org/chromium/chrome/browser/payments/AndroidPaymentApp.java
[modify] https://crrev.com/b739440826fb34eaed9931838845e3adc32727ac/chrome/android/java/src/org/chromium/chrome/browser/payments/AutofillPaymentApp.java
[modify] https://crrev.com/b739440826fb34eaed9931838845e3adc32727ac/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentApp.java
[modify] https://crrev.com/b739440826fb34eaed9931838845e3adc32727ac/chrome/android/java/src/org/chromium/chrome/browser/payments/PaymentRequestImpl.java
[modify] https://crrev.com/b739440826fb34eaed9931838845e3adc32727ac/chrome/android/java/src/org/chromium/chrome/browser/payments/ServiceWorkerPaymentApp.java
[modify] https://crrev.com/b739440826fb34eaed9931838845e3adc32727ac/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestTestCommon.java