Adding MimeHandlerView.

extensions/common/switches.cc

Index: extensions/common/switches.cc
diff --git a/extensions/common/switches.cc b/extensions/common/switches.cc
index afa05b18da0c121e5cb51609520717e406a338bc..a6f8cffa6d7f80dadd93587d0451f757fec2cfcb 100644
--- a/extensions/common/switches.cc
+++ b/extensions/common/switches.cc
@@ -46,6 +46,10 @@ const char kEnableExperimentalExtensionApis[] =
 const char kEnableExtensionActionRedesign[] =
     "enable-extension-action-redesign";
 
+// Hack so that feature switch can work with about_flags. See
+// kEnableScriptsRequireAction.
+const char kEnableMimeHandlerView[] = "enable-mime-handler-view";
+
 // Enables extensions to hide bookmarks UI elements.
 const char kEnableOverrideBookmarksUI[] = "enable-override-bookmarks-ui";
 
@@ -75,6 +79,9 @@ const char kExtensionsOnChromeURLs[] = "extensions-on-chrome-urls";
 // Whether to force developer mode extensions highlighting.
 const char kForceDevModeHighlighting[] = "force-dev-mode-highlighting";
 
+// Whether or not mime handler view guests are enabled.
+const char kMimeHandlerView[] = "mime-handler-view";
+
 // Notify the user and require consent for extensions running scripts.
 // Appending --scripts-require-action=1 has the same effect as
 // --enable-scripts-require-action (see below).