[sync] Reland - Replace FakeServer's implementation with LoopbackServer invocations.

components/sync/engine_impl/loopback_server/loopback_server.h

Index: components/sync/engine_impl/loopback_server/loopback_server.h
diff --git a/components/sync/engine_impl/loopback_server/loopback_server.h b/components/sync/engine_impl/loopback_server/loopback_server.h
index a69c99e4ac7c7da84751a21b88d3da0642352830..d9fac61c1fca92c69fe6dfea69a0766e5bc97809 100644
--- a/components/sync/engine_impl/loopback_server/loopback_server.h
+++ b/components/sync/engine_impl/loopback_server/loopback_server.h
@@ -22,11 +22,25 @@
 #include "components/sync/protocol/loopback_server.pb.h"
 #include "components/sync/protocol/sync.pb.h"
 
+namespace fake_server {
+class FakeServer;
+}
+
 namespace syncer {
 
 // A loopback version of the Sync server used for local profile serialization.
 class LoopbackServer {
  public:
+  class ObserverForTests {
+   public:
+    virtual ~ObserverForTests() {}
+
+    // Called after the server has processed a successful commit. The types
+    // updated as part of the commit are passed in |committed_model_types|.
+    virtual void OnCommit(const std::string& committer_id,
+                          syncer::ModelTypeSet committed_model_types) = 0;
+  };
+
   explicit LoopbackServer(const base::FilePath& persistent_file);
   virtual ~LoopbackServer();
 
@@ -40,6 +54,9 @@ class LoopbackServer {
                      std::string* response);
 
  private:
+  // Allow the FakeServer decorator to inspect the internals of this class.
+  friend class fake_server::FakeServer;
+
   using EntityMap =
       std::map<std::string, std::unique_ptr<LoopbackServerEntity>>;
 
@@ -102,6 +119,35 @@ class LoopbackServer {
   // Returns the store birthday.
   std::string GetStoreBirthday() const;
 
+  // Returns all entities stored by the server of the given |model_type|.
+  // This method is only used in tests.
+  std::vector<sync_pb::SyncEntity> GetSyncEntitiesByModelType(
+      syncer::ModelType model_type);
+
+  // Creates a DicionaryValue representation of all entities present in the
+  // server. The dictionary keys are the strings generated by ModelTypeToString
+  // and the values are ListValues containing StringValue versions of entity
+  // names. Used by test to verify the contents of the server state.
+  std::unique_ptr<base::DictionaryValue> GetEntitiesAsDictionaryValue();
+
+  // Modifies the entity on the server with the given |id|. The entity's
+  // EntitySpecifics are replaced with |updated_specifics| and its version is
+  // updated to n+1. If the given |id| does not exist or the ModelType of
+  // |updated_specifics| does not match the entity, false is returned.
+  // Otherwise, true is returned to represent a successful modification.
+  //
+  // This method sometimes updates entity data beyond EntitySpecifics. For
+  // example, in the case of a bookmark, changing the BookmarkSpecifics title
+  // field will modify the top-level entity's name field.
+  // This method is only used in tests.
+  bool ModifyEntitySpecifics(const std::string& id,
+                             const sync_pb::EntitySpecifics& updated_specifics);
+
+  // This method is only used in tests.
+  bool ModifyBookmarkEntity(const std::string& id,
+                            const std::string& parent_id,
+                            const sync_pb::EntitySpecifics& updated_specifics);
+
   // Serializes the server state to |proto|.
   void SerializeState(sync_pb::LoopbackServerProto* proto) const;
 
@@ -114,6 +160,10 @@ class LoopbackServer {
   // Loads all entities and server state from a protobuf file in |filename|.
   bool LoadStateFromFile(const base::FilePath& filename);
 
+  void set_observer_for_tests(ObserverForTests* observer) {
+    observer_for_tests_ = observer;
+  }
+
   // This is the last version number assigned to an entity. The next entity will
   // have a version number of version_ + 1.
   int64_t version_;
@@ -128,6 +178,9 @@ class LoopbackServer {
 
   // Used to verify that LoopbackServer is only used from one thread.
   base::ThreadChecker thread_checker_;
+
+  // Used to observe the completion of commit messages for the sake of testing.
+  ObserverForTests* observer_for_tests_;
 };
 
 }  // namespace syncer