Sync: Support multiple setup UIs.

components/sync_driver/sync_service.h

Index: components/sync_driver/sync_service.h
diff --git a/components/sync_driver/sync_service.h b/components/sync_driver/sync_service.h
index 4ca8b42e870f5ea9939a74acd6d0cd43f8746cdd..f1594facf35146ef959721195c3759966b4e7a87 100644
--- a/components/sync_driver/sync_service.h
+++ b/components/sync_driver/sync_service.h
@@ -8,7 +8,7 @@
 #include <memory>
 #include <string>
 
-#include "base/callback_forward.h"
+#include "base/callback.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ -46,6 +46,15 @@ class LocalDeviceInfoProvider;
 class OpenTabsUIDelegate;
 class SyncClient;
 
+class SyncSetupInProgressHandle {
+ public:
+  explicit SyncSetupInProgressHandle(base::Closure on_destroy);
+  ~SyncSetupInProgressHandle();
+
+ private:
+  base::Closure on_destroy_;
+};
+
 class SyncService : public DataTypeEncryptionHandler {
  public:
   // Used to specify the kind of passphrase with which sync data is encrypted.
@@ -67,7 +76,6 @@ class SyncService : public DataTypeEncryptionHandler {
   // Status of sync server connection, sync token and token request.
   struct SyncTokenStatus {
     SyncTokenStatus();
-    ~SyncTokenStatus();
 
     // Sync server connection status reported by sync backend.
     base::Time connection_status_update_time;
@@ -176,12 +184,12 @@ class SyncService : public DataTypeEncryptionHandler {
   // Called by the UI to notify the SyncService that UI is visible so it will
   // not start syncing. This tells sync whether it's safe to start downloading
   // data types yet (we don't start syncing until after sync setup is complete).
-  // The UI calls this as soon as any part of the signin wizard is displayed
-  // (even just the login UI).
-  // If |setup_in_progress| is false, this also kicks the sync engine to ensure
-  // that data download starts. In this case, |ReconfigureDatatypeManager| will
-  // get triggered.
-  virtual void SetSetupInProgress(bool setup_in_progress) = 0;
+  // The UI calls this and holds onto the instance for as long as any part of
+  // the signin wizard is displayed (even just the login UI).
+  // When the last outstanding handle is deleted, this kicks off the sync engine
+  // to ensure that data download starts. In this case,
+  // |ReconfigureDatatypeManager| will get triggered.
+  std::unique_ptr<SyncSetupInProgressHandle> GetSetupInProgressHandle();
 
   // Used by tests.
   virtual bool IsSetupInProgress() const = 0;
@@ -325,9 +333,19 @@ class SyncService : public DataTypeEncryptionHandler {
           callback) = 0;
 
  protected:
-  SyncService() {}
+  friend class SyncSetupInProgressHandle;
+
+  SyncService() : outstanding_setup_in_progress_handles_(0) {}
+
+  // Called internally by the GetSetupInProgressHandle mechanism.
+  // This should not be called directly (except by the Android wrapper).
+  virtual void SetSetupInProgress(bool setup_in_progress) = 0;
+
+  int outstanding_setup_in_progress_handles_;
 
  private:
+  void OnSetupInProgressHandleDestroyed();
+
   DISALLOW_COPY_AND_ASSIGN(SyncService);
 };