Introduce the plumbing necessary to report Unrecoverable error from model safe workers.

chrome/browser/sync/engine/syncer_types.h

Index: chrome/browser/sync/engine/syncer_types.h
diff --git a/chrome/browser/sync/engine/syncer_types.h b/chrome/browser/sync/engine/syncer_types.h
index 54d4b3e2974d295d9c50e17bd5db956f11a6bcf8..9563c1182272cb812bf846c446f3cfd851b2177e 100644
--- a/chrome/browser/sync/engine/syncer_types.h
+++ b/chrome/browser/sync/engine/syncer_types.h
@@ -10,7 +10,9 @@
 #include <string>
 #include <vector>
 
+#include "base/location.h"
 #include "base/observer_list.h"
+#include "chrome/browser/sync/sessions/unrecoverable_error_info.h"
 #include "chrome/browser/sync/syncable/model_type.h"
 
 namespace syncable {
@@ -39,7 +41,10 @@ enum UpdateAttemptResponse {
   // forward progress on this node, but because the passphrase may not arrive
   // until later we don't want to get the syncer stuck. See UpdateApplicator
   // for how this is handled.
-  CONFLICT_ENCRYPTION
+  CONFLICT_ENCRYPTION,
+
+  // Failed to apply the update because of an error.
+  FAILED_UPDATE
 };
 
 enum ServerUpdateProcessingResult {
@@ -109,13 +114,24 @@ struct SyncEngineEvent {
     // This event is sent when we receive an actionable error. It is upto
     // the listeners to figure out the action to take using the snapshot sent.
     ACTIONABLE_ERROR,
+
+    // This event is sent when syncer receives an unrecoverable error.
+    UNRECOVERABLE_ERROR,
   };
 
   explicit SyncEngineEvent(EventCause cause);
+
+  // Use this constructor in case of unrecoverable error.
+  SyncEngineEvent(
+      const tracked_objects::Location& unrecoverable_error_location,
+      const std::string& message);
   ~SyncEngineEvent();
 
   EventCause what_happened;
 
+  // Bookkeeping for unrecoverable errors.
+  sessions::UnrecoverableErrorInfo unrecoverable_error_info;
+
   // The last session used for syncing.
   const sessions::SyncSessionSnapshot* snapshot;