PaymentApp: Add classes for supporting Web Based Payment Apps
This adds an application class, an instrument class and a skeleton
bridging class which can later be implemented to communicate with the
service worker class in C++.
The app factory class has been extended to create instances of the new
web based payment apps in addition to the existing autofill payment app.
BUG=669876
Review-Url: https://codereview.chromium.org/2526293003
Cr-Commit-Position: refs/heads/master@{#436274}
11 files changed
