[Sync] Adding integration tests for USS encryption and fixing a worker bug.

components/sync/engine_impl/model_type_worker.h

Index: components/sync/engine_impl/model_type_worker.h
diff --git a/components/sync/engine_impl/model_type_worker.h b/components/sync/engine_impl/model_type_worker.h
index 46a69b6560b9fac25c1fc10a39ec8bf0356dfa4c..ffb23deb9cad80dc57e1586bfe48bc146f9acb60 100644
--- a/components/sync/engine_impl/model_type_worker.h
+++ b/components/sync/engine_impl/model_type_worker.h
@@ -109,6 +109,10 @@ class ModelTypeWorker : public UpdateHandler,
   // settings in a good state.
   bool CanCommitItems() const;
 
+  // Returns true if this type should stop communicating because of outstanding
+  // encyrption issues. Must wait for keys to be updated.

[maxbogue, 2016/10/11 15:56:39]

"encryption"

[skym, 2016/10/11 16:41:00]

Spelling it hard :(

+  bool BlockForEncryption() const;
+
   // Takes |commit_entity| populated from fields of WorkerEntityTracker and
   // adjusts some fields before committing to server. Adjustments include
   // generating client-assigned ID, encrypting data, etc.
@@ -173,6 +177,11 @@ class ModelTypeWorker : public UpdateHandler,
   // they can all be sent to the processor at once.
   UpdateResponseDataList pending_updates_;
 
+  // Flag to remember if all entities in get updates responses have been
+  // successfully decrypted or not. Data stops flowing out of the worker when
+  // this flag is set to false.
+  bool decrypted_everything_;

[maxbogue, 2016/10/11 15:56:39]

I keep reading this as "decrypt_everything_". Could you make it
"everything_decrypted_" instead so it's harder to misread?

[skym, 2016/10/11 16:41:00]

Done.

+
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<ModelTypeWorker> weak_ptr_factory_;
 };