PaymentApp: Implement GetAllManifests() in PaymentAppContext.

content/browser/payments/payment_app_context_impl.h

Index: content/browser/payments/payment_app_context_impl.h
diff --git a/content/browser/payments/payment_app_context_impl.h b/content/browser/payments/payment_app_context_impl.h
index 824b5c27a7a5cd7f0e8216cfc961e720f49feaa6..8785bbcc8bd9945f3cba74bb5bb05876e2cefde6 100644
--- a/content/browser/payments/payment_app_context_impl.h
+++ b/content/browser/payments/payment_app_context_impl.h
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "components/payments/payment_app.mojom.h"
+#include "content/browser/payments/payment_app_database.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/payment_app_context.h"
 
@@ -66,12 +67,11 @@ class CONTENT_EXPORT PaymentAppContextImpl
   PaymentAppDatabase* payment_app_database() const;
 
   // PaymentAppContext implementation:
+  // Should be accessed only on the UI thread.
   void GetAllManifests(const GetAllManifestsCallback& callback) override;
 
- protected:
-  friend class PaymentAppManagerTest;
-
  private:
+  friend class PaymentAppContentUnitTestBase;
   friend class base::RefCountedThreadSafe<PaymentAppContextImpl>;
   ~PaymentAppContextImpl() override;
 
@@ -84,6 +84,10 @@ class CONTENT_EXPORT PaymentAppContextImpl
   void ShutdownOnIO();
   void DidShutdown();
 
+  void GetAllManifestsOnIO(const GetAllManifestsCallback& callback);
+  void DidGetAllManifestsOnIO(const GetAllManifestsCallback& callback,
+                              PaymentAppDatabase::Manifests manifests);
+
   // Only accessed on the IO thread.
   std::unique_ptr<PaymentAppDatabase> payment_app_database_;