PaymentHandler: Implement GetAllPaymentApps().

components/payments/mojom/payment_app.mojom

Index: components/payments/mojom/payment_app.mojom
diff --git a/components/payments/mojom/payment_app.mojom b/components/payments/mojom/payment_app.mojom
index b43c771988ff6e274b6174ab909a22d788df4842..09d395b0952cceea95c5ac348728736051a45ed3 100644
--- a/components/payments/mojom/payment_app.mojom
+++ b/components/payments/mojom/payment_app.mojom
@@ -37,6 +37,9 @@ enum PaymentHandlerStatus {
 };
 
 struct PaymentInstrument {
+  int64 registration_id;

[Tom Sepez, 2017/05/09 17:07:21]

Where does this ID come from?  Is unique to a renderer?  Is it guessable?  If
some other renderer guesses this ID, what's the worst that can happen?

[zino, 2017/05/09 17:16:57]

These three members are only used in browser side.
Is this usage restricted? (if do not allow this way, we will write a new
additional class?)
If not so, I leave a comment here like that:
"These three members are only used in browser side.. do not use these members in
renderer side blah blah.."

[Tom Sepez, 2017/05/09 17:37:25]

I'm not sure the comment is helpful.  I'm also not sure what you mean by "only
used browser side".  If so, why are they being passed across mojo?

[zino, 2017/05/10 17:54:42]

I removed these members in mojom and then add a new struct in public directory.
(payment_instrument.h and .cc)

So, there is no mojom change in this patch.

+  string? instrument_key;
+  url.mojom.Url origin;
   string name;
   array<string> enabled_methods;
   string stringified_capabilities;