Replace calls to 3-arg SyncData::CreateLocalData with 5-arg version.

sync/api/attachments/attachment_service_proxy.h

 // Copyright 2014 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 SYNC_API_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
 #define SYNC_API_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/sequenced_task_runner.h"
 #include "base/task_runner.h"
 #include "sync/api/attachments/attachment.h"
 #include "sync/api/attachments/attachment_service.h"
 #include "sync/base/sync_export.h"
 
 namespace syncer {
 
 class SyncData;
 
 // AttachmentServiceProxy wraps an AttachmentService allowing multiple threads
-// to share the wrapped AttachmentService.
+// to share the wrapped AttachmentService and invoke its methods in the
+// appropriate thread.
 //
 // Callbacks passed to methods on this class will be invoked in the same thread
 // from which the method was called.
 //
 // This class does not own its wrapped AttachmentService object.  This class
 // holds a WeakPtr to the wrapped object.  Once the the wrapped object is
 // destroyed, method calls on this object will be no-ops.
 //
-//  Users of this class should take care to destroy the wrapped object on the
-//  correct thread (wrapped_task_runner).
+// Users of this class should take care to destroy the wrapped object on the
+// correct thread (wrapped_task_runner).
 //
-// This class is thread-safe.
+// This class is thread-safe and is designed to be passed by const-ref.
 class SYNC_EXPORT AttachmentServiceProxy : public AttachmentService {
  public:
   // Default copy and assignment are welcome.
 
   // Construct an invalid AttachmentServiceProxy.
   AttachmentServiceProxy();
 
   // Construct an AttachmentServiceProxy that forwards calls to |wrapped| on the
   // |wrapped_task_runner| thread.
+  //
+  // Note, this object does not own |wrapped|.  When |wrapped| is destroyed,
+  // calls to this object become no-ops.
   AttachmentServiceProxy(
       const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
-      base::WeakPtr<syncer::AttachmentService> wrapped);
+      const base::WeakPtr<syncer::AttachmentService>& wrapped);
 
   virtual ~AttachmentServiceProxy();
 
   // AttachmentService implementation.
-  virtual void GetOrDownloadAttachments(const AttachmentIdList& attachment_ids,
-                                        const GetOrDownloadCallback& callback)
-      OVERRIDE;
+  virtual void GetOrDownloadAttachments(
+      const AttachmentIdList& attachment_ids,
+      const GetOrDownloadCallback& callback) OVERRIDE;
   virtual void DropAttachments(const AttachmentIdList& attachment_ids,
                                const DropCallback& callback) OVERRIDE;
   virtual void OnSyncDataAdd(const SyncData& sync_data) OVERRIDE;
   virtual void OnSyncDataDelete(const SyncData& sync_data) OVERRIDE;
   virtual void OnSyncDataUpdate(const AttachmentIdList& old_attachment_ids,
                                 const SyncData& updated_sync_data) OVERRIDE;
 
+ protected:
+  // Core does the work of proxying calls to AttachmentService methods from one
+  // thread to another so AttachmentServiceProxy can be an easy-to-use,
+  // non-ref-counted A ref-counted class.
+  //
+  // Callback from AttachmentService are proxied back using free functions
+  // defined in the .cc file (ProxyFooCallback functions).
+  //
+  // Core is ref-counted because we want to allow AttachmentServiceProxy to be
+  // copy-constructable while allowing for different implementations of Core
+  // (e.g. one type of core might own the wrapped AttachmentService).
+  //
+  // Calls to objects of this class become no-ops once its wrapped object is
+  // destroyed.
+  class SYNC_EXPORT Core : public AttachmentService,
+                           public base::RefCountedThreadSafe<Core> {
+   public:
+    // Construct an AttachmentServiceProxyCore that forwards calls to |wrapped|.
+    Core(const base::WeakPtr<syncer::AttachmentService>& wrapped);
+
+    // AttachmentService implementation.
+    virtual void GetOrDownloadAttachments(
+        const AttachmentIdList& attachment_ids,
+        const GetOrDownloadCallback& callback) OVERRIDE;
+    virtual void DropAttachments(const AttachmentIdList& attachment_ids,
+                                 const DropCallback& callback) OVERRIDE;
+    virtual void OnSyncDataAdd(const SyncData& sync_data) OVERRIDE;
+    virtual void OnSyncDataDelete(const SyncData& sync_data) OVERRIDE;
+    virtual void OnSyncDataUpdate(const AttachmentIdList& old_attachment_ids,
+                                  const SyncData& updated_sync_data) OVERRIDE;
+
+   protected:
+    friend class base::RefCountedThreadSafe<Core>;
+    virtual ~Core();
+
+   private:
+    base::WeakPtr<AttachmentService> wrapped_;
+
+    DISALLOW_COPY_AND_ASSIGN(Core);
+  };
+
+  // Used in tests to create an AttachmentServiceProxy with a custom Core.
+  AttachmentServiceProxy(
+      const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
+      const scoped_refptr<Core>& core);
+
  private:
   scoped_refptr<base::SequencedTaskRunner> wrapped_task_runner_;
-  // wrapped_ must only be dereferenced on the wrapped_task_runner_ thread.
-  base::WeakPtr<AttachmentService> wrapped_;
+  scoped_refptr<Core> core_;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_