Move LaunchContainer enum to extension_constants.h.

extensions/common/constants.h

Index: extensions/common/constants.h
diff --git a/extensions/common/constants.h b/extensions/common/constants.h
index a071ca968544a5477c01eb0a98ab165d3614a16c..3113a17e9fdaee9936bd2c16d1fa13fc6c35f6cc 100644
--- a/extensions/common/constants.h
+++ b/extensions/common/constants.h
@@ -83,18 +83,6 @@ extern const char kStateStoreName[];
 // rules are stored.
 extern const char kRulesStoreName[];
 
-// Don't remove items or change the order of this enum.  It's used in
-// histograms and preferences.
-// TODO(derat): Move this to chrome/browser/extensions/launch_util.h?
-enum LaunchContainer {
-  LAUNCH_WINDOW,
-  LAUNCH_PANEL,
-  LAUNCH_TAB,
-  // For platform apps, which don't actually have a container (they just get a
-  // "onLaunched" event).
-  LAUNCH_NONE
-};
-
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_CONSTANTS_H_