Create an AutofillBackend interface

components/autofill/browser/webdata/autofill_webdata_backend.h

Index: components/autofill/browser/webdata/autofill_webdata_backend.h
diff --git a/components/autofill/browser/webdata/autofill_webdata_backend.h b/components/autofill/browser/webdata/autofill_webdata_backend.h
index b1ab6d63b089552b6c7f2106f0384181589e0374..39e6709639c1e866041d744e0ca4b6e3c86c4659 100644
--- a/components/autofill/browser/webdata/autofill_webdata_backend.h
+++ b/components/autofill/browser/webdata/autofill_webdata_backend.h
@@ -6,14 +6,18 @@
 #define COMPONENTS_AUTOFILL_BROWSER_WEBDATA_AUTOFILL_WEBDATA_BACKEND_H_
 
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "components/autofill/browser/webdata/autofill_webdata.h"
+#include "components/autofill/browser/webdata/syncable_service_backend.h"
 #include "components/autofill/common/form_field_data.h"
 #include "components/webdata/common/web_data_results.h"
 #include "components/webdata/common/web_data_service_base.h"
 #include "components/webdata/common/web_data_service_consumer.h"
 #include "components/webdata/common/web_database.h"
 
+class WebDataServiceBackend;
+
 namespace autofill {
 
 class AutofillChange;
@@ -28,9 +32,23 @@ class CreditCard;
 // WebDataService.
 class AutofillWebDataBackend
     : public base::RefCountedThreadSafe<AutofillWebDataBackend,
-          content::BrowserThread::DeleteOnDBThread> {
+          content::BrowserThread::DeleteOnDBThread>,
+      public SyncableServiceBackend {
  public:
-  AutofillWebDataBackend();
+  // |web_db_backend| is used to access the WebDatabase directly for
+  // Sync-related operations. |on_changed_callback| is a closure which can be
+  // used to notify the UI thread of changes initiated by Sync.

[Ilya Sherman, 2013/05/08 00:39:06]

Please document that |on_changed_callback| might be Run() multiple times.

[Cait (Slow), 2013/05/08 19:16:01]

Done.

+  AutofillWebDataBackend(scoped_refptr<WebDataServiceBackend> web_db_backend,

[Ilya Sherman, 2013/05/08 00:39:06]

nit: Please name this variable |web_database_backend| to match the member
variable name.  Also, why does the class name use "DataService" whereas the
variable name is "database"?

[Cait (Slow), 2013/05/08 19:16:01]

Adding a todo to rename WebDataServiceBackend to WebDatabaseBackend. This was a
mistake on my part, and now that the class is used by more than just the
WebDatabaseService, it should definitely be fixed to avoid further confusion. 

+                         const base::Closure& on_changed_callback);
+
+  // SyncableServiceBackend implementation.
+  virtual void AddObserver(AutofillWebDataServiceObserverOnDBThread* observer)
+    OVERRIDE;

[Ilya Sherman, 2013/05/08 00:39:06]

nit: Indent two more spaces.

[Cait (Slow), 2013/05/08 19:16:01]

Done.

+  virtual void RemoveObserver(
+    AutofillWebDataServiceObserverOnDBThread* observer) OVERRIDE;

[Ilya Sherman, 2013/05/08 00:39:06]

nit: Indent two more spaces.

[Cait (Slow), 2013/05/08 19:16:01]

Done.

+  virtual WebDatabase* GetDatabaseOnDB() OVERRIDE;
+  virtual void RemoveExpiredFormElementsWrapper() OVERRIDE;
+  virtual void NotifyOfMultipleAutofillChanges() OVERRIDE;
 
   // Adds form fields to the web database.
   WebDatabase::State AddFormElements(const std::vector<FormFieldData>& fields,
@@ -95,12 +113,6 @@ class AutofillWebDataBackend
       const base::Time& delete_end,
       WebDatabase* db);
 
-  // Add an observer to be notified of changes on the DB thread.
-  void AddObserver(AutofillWebDataServiceObserverOnDBThread* observer);
-
-  // Remove an observer.
-  void RemoveObserver(AutofillWebDataServiceObserverOnDBThread* observer);
-
  protected:
   virtual ~AutofillWebDataBackend();
 
@@ -120,6 +132,12 @@ class AutofillWebDataBackend
 
   ObserverList<AutofillWebDataServiceObserverOnDBThread> db_observer_list_;
 
+  // Ptr to WebDataServiceBackend to allow direct access to DB.

[Ilya Sherman, 2013/05/08 00:39:06]

nit: Omit "Ptr to"

[Cait (Slow), 2013/05/08 19:16:01]

Done.

+  // TODO(caitkp): Make it so nobody but us needs direct DB access anymore.
+  scoped_refptr<WebDataServiceBackend> web_database_backend_;
+
+  scoped_ptr<base::Closure> on_changed_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(AutofillWebDataBackend);
 };