PaymentHandler: Implement GetAllPaymentApps().

content/public/browser/payment_app_provider.h

Index: content/public/browser/payment_app_provider.h
diff --git a/content/public/browser/payment_app_provider.h b/content/public/browser/payment_app_provider.h
index 9a86d0195870e124d138380267585cdb010ee085..742a3eb996f5a9f9826c59562806be0facc57066 100644
--- a/content/public/browser/payment_app_provider.h
+++ b/content/public/browser/payment_app_provider.h
@@ -33,15 +33,21 @@ class CONTENT_EXPORT PaymentAppProvider {
       std::pair<int64_t, payments::mojom::PaymentAppManifestPtr>;
   using Manifests = std::vector<ManifestWithID>;
 
+  using Instruments = std::vector<payments::mojom::PaymentInstrumentPtr>;
+  using PaymentApps = std::map<GURL, Instruments>;
+
   // TODO(zino): Consider to use base::OnceCallback instead of base::Callback.
   // Please see: http://crbug.com/704193
   using GetAllManifestsCallback = base::Callback<void(Manifests)>;
+  using GetAllPaymentAppsCallback = base::OnceCallback<void(PaymentApps)>;
   using InvokePaymentAppCallback =
       base::Callback<void(payments::mojom::PaymentAppResponsePtr)>;
 
   // Should be accessed only on the UI thread.
   virtual void GetAllManifests(BrowserContext* browser_context,
                                const GetAllManifestsCallback& callback) = 0;
+  virtual void GetAllPaymentApps(BrowserContext* browser_context,
+                                 GetAllPaymentAppsCallback callback) = 0;
   virtual void InvokePaymentApp(
       BrowserContext* browser_context,
       int64_t registration_id,