[Payments] Implement openWindow for service worker based payment handler

content/common/service_worker/service_worker_messages.h

Index: content/common/service_worker/service_worker_messages.h
diff --git a/content/common/service_worker/service_worker_messages.h b/content/common/service_worker/service_worker_messages.h
index ef5a82603f3ad008980345e9460d5ba090865388..6ad80b0dd8c72b122582f6a764685038594ff078 100644
--- a/content/common/service_worker/service_worker_messages.h
+++ b/content/common/service_worker/service_worker_messages.h
@@ -271,8 +271,15 @@ IPC_MESSAGE_ROUTED2(ServiceWorkerHostMsg_SetCachedMetadata,
 // clear the cache associated with |url|.
 IPC_MESSAGE_ROUTED1(ServiceWorkerHostMsg_ClearCachedMetadata, GURL /* url */)
 
-// Ask the browser to open a tab/window (renderer->browser).
-IPC_MESSAGE_ROUTED2(ServiceWorkerHostMsg_OpenWindow,
+// Ask the browser to open a tab/window (renderer->browser) for
+// clients.openWindow.
+IPC_MESSAGE_ROUTED2(ServiceWorkerHostMsg_OpenWindowForClients,
+                    int /* request_id */,
+                    GURL /* url */)
+
+// Ask the browser to open a tab/window (renderer->browser) for payment handler,
+// i.e., PaymentRequestEvent.openWindow().
+IPC_MESSAGE_ROUTED2(ServiceWorkerHostMsg_OpenWindowForPaymentHandler,

[dcheng, 2017/06/05 21:04:47]

Nit: I think it would be clearer if the messages just encoded what they did,
rather than what they're used for.

e.g.

ServiceWorkerHostMsg_OpenNewTab
ServiceWorkerHostMsg_OpenNewPopup

[gogerald1, 2017/06/05 22:26:44]

The sender and receiver of these messages both specified usage in their name,
and these messages are only been used in service worker, it looks a little
easier to read with usage in name, so I'd like to keep them if you don't mind.

[dcheng, 2017/06/06 00:25:48]

There's nothing payments specific about this though. The only distinction here
is the window open disposition--without that in the name, I have to go look at
the IPC handler to figure that nothing particularly interesting is happening.

It also makes the sending side clearer--it's immediately obvious what kind of
window is being opened, etc.

In fact, I would say that the new methods in content/renderer should be named to
reflect the IPC messages (and their actual result). I'm pretty sure there's a
style tip for this somewhere as well, but I can't find it atm.

[gogerald1, 2017/06/06 01:25:48]

Done.

                     int /* request_id */,
                     GURL /* url */)