sync: Add pre-commit update avoidance mode + flag

chrome/common/chrome_switches.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Defines all the command-line switches used by Chrome.
 
 #ifndef CHROME_COMMON_CHROME_SWITCHES_H_
 #define CHROME_COMMON_CHROME_SWITCHES_H_
 
 #include "build/build_config.h"
@@ skipping 340 matching lines @@
 extern const char kSuggestionNtpLinearFilter[];
 extern const char kSyncAllowInsecureXmppConnection[];
 extern const char kSyncInvalidateXmppLogin[];
 extern const char kSyncShortInitialRetryOverride[];
 extern const char kSyncNotificationHostPort[];
 extern const char kSyncServiceURL[];
 extern const char kSyncThrowUnrecoverableError[];
 extern const char kSyncTrySsltcpFirstForXmpp[];
 extern const char kSyncEnableDeferredStartup[];
 extern const char kSyncDisableOAuth2Token[];
+extern const char kSyncEnableGetUpdateAvoidance[];
 extern const char kSyncfsEnableDirectoryOperation[];
 extern const char kTabBrowserDragging[];
 extern const char kTabCapture[];
 extern const char kTestName[];
 extern const char kTestType[];
 extern const char kTestingChannelID[];
 extern const char kTrackActiveVisitTime[];
 extern const char kTranslateScriptURL[];
 extern const char kTrustedSpdyProxy[];
 extern const char kTryChromeAgain[];
@@ skipping 79 matching lines @@
 #else
 extern const char kEnablePrintPreview[];
 #endif
 
 // DON'T ADD RANDOM STUFF HERE. Put it in the main section above in
 // alphabetical order, or in one of the ifdefs (also in order in each section).
 
 }  // namespace switches
 
 #endif  // CHROME_COMMON_CHROME_SWITCHES_H_