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

chrome/browser/sync/glue/sync_backend_host.cc

Index: chrome/browser/sync/glue/sync_backend_host.cc
diff --git a/chrome/browser/sync/glue/sync_backend_host.cc b/chrome/browser/sync/glue/sync_backend_host.cc
index ff5374dc4529083c118e3a82e5ec888a1cdccd84..89b4f7120525e8c0fe773c8459b4819825f8da6c 100644
--- a/chrome/browser/sync/glue/sync_backend_host.cc
+++ b/chrome/browser/sync/glue/sync_backend_host.cc
@@ -525,6 +525,18 @@ void SyncBackendHost::Core::OnActionableError(
                         sync_error));
 }
 
+void SyncBackendHost::Core::OnUnrecoverableError(
+    const tracked_objects::Location& location,
+    const std::string& message) {
+  DCHECK_EQ(MessageLoop::current(), sync_loop_);
+  host_->frontend_loop_->PostTask(
+      FROM_HERE,
+      NewRunnableMethod(this, &Core::HandleUnrecoverableErrorOnFrontendLoop,
+                        location,
+                        message));
+
+}
+
 SyncBackendHost::Core::DoInitializeOptions::DoInitializeOptions(
     MessageLoop* sync_loop,
     SyncBackendRegistrar* registrar,
@@ -751,6 +763,16 @@ void SyncBackendHost::Core::HandleActionableErrorEventOnFrontendLoop(
   host_->frontend_->OnActionableError(sync_error);
 }
 
+void SyncBackendHost::Core::HandleUnrecoverableErrorOnFrontendLoop(
+    const tracked_objects::Location& location,
+    const std::string& message) {
+  if (!host_ || !host_->frontend_)
+    return;
+  DCHECK_EQ(MessageLoop::current(), host_->frontend_loop_);
+  host_->frontend_->OnUnrecoverableError(location, message);
+}
+
+
 void SyncBackendHost::Core::HandleAuthErrorEventOnFrontendLoop(
     const GoogleServiceAuthError& new_auth_error) {
   if (!host_ || !host_->frontend_)