[Sync] Make BackendMigrator not wait for full sync cycles

chrome/browser/sync/glue/sync_backend_host.h

Index: chrome/browser/sync/glue/sync_backend_host.h
diff --git a/chrome/browser/sync/glue/sync_backend_host.h b/chrome/browser/sync/glue/sync_backend_host.h
index 5a0b0f638af4abbf0f5a731cc6ee76937ec75084..33570604509ce58ae7bb87678bd728fed6ebb282 100644
--- a/chrome/browser/sync/glue/sync_backend_host.h
+++ b/chrome/browser/sync/glue/sync_backend_host.h
@@ -117,7 +117,7 @@ class SyncBackendHost {
   // Create a SyncBackendHost with a reference to the |frontend| that it serves
   // and communicates to via the SyncFrontend interface (on the same thread
   // it used to call the constructor).
-  explicit SyncBackendHost(Profile* profile);
+  SyncBackendHost(const std::string& name, Profile* profile);
   // For testing.
   // TODO(skrul): Extract an interface so this is not needed.
   SyncBackendHost();
@@ -179,6 +179,10 @@ class SyncBackendHost {
 
   syncable::ModelTypeSet GetEncryptedDataTypes() const;
 
+  // Returns the set of types for which there is no sync data.
+  // Overrideable for testing.
+  virtual syncable::ModelTypeSet GetUnsyncedDataTypes() const;
+
   // Activates change processing for the given data type.  This must
   // be called synchronously with the data type's model association so
   // no changes are dropped between model association and change
@@ -248,7 +252,7 @@ class SyncBackendHost {
   class Core : public base::RefCountedThreadSafe<SyncBackendHost::Core>,
                public sync_api::SyncManager::Observer {
    public:
-    Core(Profile* profile, SyncBackendHost* backend);
+    Core(const std::string& name, SyncBackendHost* backend);
 
     // SyncManager::Observer implementation.  The Core just acts like an air
     // traffic controller here, forwarding incoming messages to appropriate
@@ -437,7 +441,8 @@ class SyncBackendHost {
 
     void FinishConfigureDataTypesOnFrontendLoop();
 
-    Profile* profile_;
+    // Name used for debugging.
+    const std::string name_;
 
     // Our parent SyncBackendHost
     SyncBackendHost* host_;
@@ -523,7 +528,10 @@ class SyncBackendHost {
   // to safely talk back to the SyncFrontend.
   MessageLoop* const frontend_loop_;
 
-  Profile* profile_;
+  Profile* const profile_;
+
+  // Name used for debugging (set from profile_->GetDebugName()).
+  const std::string name_;
 
   sync_notifier::SyncNotifierFactory sync_notifier_factory_;