Initial skeleton for System Indicator API

chrome/common/extensions/extension_manifest_constants.cc

Index: chrome/common/extensions/extension_manifest_constants.cc
diff --git a/chrome/common/extensions/extension_manifest_constants.cc b/chrome/common/extensions/extension_manifest_constants.cc
index e58ecdcfb7871901f7480d5c09547f96c51e7116..16eae245321e3ed0035185888f53b404c6c71419 100644
--- a/chrome/common/extensions/extension_manifest_constants.cc
+++ b/chrome/common/extensions/extension_manifest_constants.cc
@@ -107,6 +107,7 @@ const char kShiftKey[] = "shiftKey";
 const char kShortcutKey[] = "shortcutKey";
 const char kSignature[] = "signature";
 const char kSuggestedKey[] = "suggested_key";
+const char kSystemIndicator[] = "system_indicator";
 const char kTheme[] = "theme";
 const char kThemeColors[] = "colors";
 const char kThemeDisplayProperties[] = "properties";
@@ -438,6 +439,8 @@ const char kInvalidScriptBadge[] =
     "Invalid value for 'script_badge'.";
 const char kInvalidSignature[] =
     "Value 'signature' is missing or invalid.";
+const char kInvalidSystemIndicator[] =
+    "Invalid value for 'system_indicator'.";
 const char kInvalidTheme[] =
     "Invalid value for 'theme'.";
 const char kInvalidThemeColors[] =