Introduce password_manager::FormFetcher

components/password_manager/core/browser/form_fetcher.h

Index: components/password_manager/core/browser/form_fetcher.h
diff --git a/components/password_manager/core/browser/form_fetcher.h b/components/password_manager/core/browser/form_fetcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..24ca598ea602858728e4d20ed7e04b9deddcf376
--- /dev/null
+++ b/components/password_manager/core/browser/form_fetcher.h
@@ -0,0 +1,77 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_FORM_FETCHER_H_
+#define COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_FORM_FETCHER_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+
+namespace autofill {
+struct PasswordForm;
+}
+
+namespace password_manager {
+
+struct InteractionsStats;
+
+// This is an API for providing stored credentials to PasswordFormManager (PFM),
+// so that PFM instances do not have to talk to PasswordStore directly. This
+// indirection allows caching of identical requests from PFM on the same origin,
+// as well as easier testing (no need to mock the whole PasswordStore when
+// testing a PFM).
+// TODO(crbug.com/621355): Actually modify the API to support fetching in the
+// FormFetcher instance.
+class FormFetcher {
+ public:
+  // State of waiting for a response from a PasswordStore. There might be
+  // multiple transitions between these states.
+  enum class State { WAITING, NOT_WAITING };
+
+  // API to be implemented by classes which want the results from FormFetcher.
+  class Consumer {
+   public:
+    virtual ~Consumer() = default;
+
+    // FormFetcher calls this method every time the state changes from WAITING
+    // to UP_TO_DATE. It fills |non_federated| with pointers to non-federated
+    // matches (pointees stay owned by FormFetcher). To access the federated
+    // matches, the consumer can simply call GetFederatedMatches().
+    // |filtered_count| is the number of non-federated forms which were
+    // filtered out by CredentialsFilter and not included in |non_federated|.
+    virtual void ProcessMatches(
+        const std::vector<const autofill::PasswordForm*>& non_federated,
+        size_t filtered_count) = 0;
+  };
+
+  FormFetcher() = default;
+
+  virtual ~FormFetcher() = default;
+
+  // Adds |consumer|, which must not be null. If the current state is
+  // UP_TO_DATE, calls ProcessMatches on the consumer immediately. Assumes that
+  // |consumer| outlives |this|.
+  virtual void AddConsumer(Consumer* consumer) = 0;
+
+  // Returns the current state of the FormFetcher
+  virtual State GetState() const = 0;
+
+  // Statistics for recent password bubble usage.
+  virtual const std::vector<const InteractionsStats*>& GetInteractionsStats()
+      const = 0;
+
+  // Federated matches obtained from the backend. Valid only if GetState()
+  // returns NOT_WAITING.
+  virtual const std::vector<const autofill::PasswordForm*>&
+  GetFederatedMatches() const = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(FormFetcher);
+};
+
+}  // namespace password_manager
+
+#endif  // COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_FORM_FETCHER_H_