Remove knowledge of Chrome-specific SyncableService classes from WebDataService.

chrome/browser/api/webdata/web_data_service_base.h

Index: chrome/browser/api/webdata/web_data_service_base.h
diff --git a/chrome/browser/api/webdata/web_data_service_base.h b/chrome/browser/api/webdata/web_data_service_base.h
index dc30fc123559bddf8d1a042a7cda0500b0ecfcac..1c92550067234f8b2f2b59a31321e70c12e794da 100644
--- a/chrome/browser/api/webdata/web_data_service_base.h
+++ b/chrome/browser/api/webdata/web_data_service_base.h
@@ -9,6 +9,7 @@
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/supports_user_data.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_source.h"
 #include "sql/init_status.h"
@@ -70,8 +71,15 @@ class WebDataServiceBase
   // DBThread.
   virtual WebDatabase* GetDatabase();
 
+  // Returns a SupportsUserData objects that may be used to store data
+  // owned by the DB thread on this object. Should be called only from
+  // the DB thread, and will be destroyed on the DB thread soon after
+  // |ShutdownOnUIThread()| is called.
+  base::SupportsUserData* GetDBUserData();
+
  protected:
   virtual ~WebDataServiceBase();
+  virtual void ShutdownOnDBThread();
 
   // Our database service.
   scoped_ptr<WebDatabaseService> wdbs_;
@@ -86,6 +94,23 @@ class WebDataServiceBase
 
   ProfileErrorCallback profile_error_callback_;
 
+  // This makes the destructor public, and thus allows us to aggregate
+  // SupportsUserData. It is private by default to prevent incorrect
+  // usage in class hierarchies where it is inherited by
+  // reference-counted objects.
+  class SupportsUserDataAggregatable : public base::SupportsUserData {
+   public:
+    SupportsUserDataAggregatable() {}
+    virtual ~SupportsUserDataAggregatable() {}
+   private:
+    DISALLOW_COPY_AND_ASSIGN(SupportsUserDataAggregatable);
+  };
+
+  // Storage for user data to be accessed only on the DB thread. May
+  // be used e.g. for SyncableService subclasses that need to be owned
+  // by this object. Is created on first call to |GetDBUserData()|.
+  scoped_ptr<SupportsUserDataAggregatable> db_thread_user_data_;
+
   void DBInitFailed(sql::InitStatus sql_status);
   void NotifyDatabaseLoadedOnUIThread();
   void DatabaseInitOnDB(sql::InitStatus status);