[Sync] Add support for performing a GetKey on startup.

sync/engine/syncer.cc

Index: sync/engine/syncer.cc
diff --git a/sync/engine/syncer.cc b/sync/engine/syncer.cc
index 66afdbcde415def66eec4d52231182855fa04978..0f7b7a0052bb539eea0e5a3425842bd4c69583fd 100644
--- a/sync/engine/syncer.cc
+++ b/sync/engine/syncer.cc
@@ -15,6 +15,7 @@
 #include "sync/engine/commit.h"
 #include "sync/engine/conflict_resolver.h"
 #include "sync/engine/download_updates_command.h"
+#include "sync/engine/get_key_command.h"
 #include "sync/engine/net/server_connection_manager.h"
 #include "sync/engine/process_commit_response_command.h"
 #include "sync/engine/process_updates_command.h"
@@ -52,6 +53,7 @@ const char* SyncerStepToString(const SyncerStep step)
 {
   switch (step) {
     ENUM_CASE(SYNCER_BEGIN);
+    ENUM_CASE(GET_ENCRYPTION_KEY);
     ENUM_CASE(DOWNLOAD_UPDATES);
     ENUM_CASE(PROCESS_CLIENT_COMMAND);
     ENUM_CASE(VERIFY_UPDATES);
@@ -106,6 +108,20 @@ void Syncer::SyncShare(sessions::SyncSession* session,
 
         next_step = DOWNLOAD_UPDATES;
         break;
+      case GET_ENCRYPTION_KEY: {
+        GetKeyCommand get_key;
+        SyncerError result = get_key.Execute(session);
+        session->mutable_status_controller()->set_last_get_key_result(result);
+        if (result == SYNCER_OK && last_step != GET_ENCRYPTION_KEY) {
+          next_step = DOWNLOAD_UPDATES;
+        } else {
+          LOG_IF(ERROR, result != SYNCER_OK)
+              << "Aborting sync cycle due to get key failure.";
+          last_step = SYNCER_END;  // Necessary for CONFIGURATION mode.
+          next_step = SYNCER_END;
+        }
+        break;
+      }
       case DOWNLOAD_UPDATES: {
         // TODO(akalin): We may want to propagate this switch up
         // eventually.