Place <webview> tag behind a flag.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index e5805674066392f3d4a54782fb3fb5b438d40dc8..5a7761b40ea9444aa8d30b6f049511f08f6ae668 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -655,6 +655,9 @@ const char kEnableWatchdog[]                = "enable-watchdog";
 // Uses WebSocket over SPDY.
 const char kEnableWebSocketOverSpdy[]       = "enable-websocket-over-spdy";
 
+// Enable <webview> in Chrome Apps.
+const char kEnableWebView[]                 = "enable-webview";
+
 // Explicitly allows additional ports using a comma-separated list of port
 // numbers.
 const char kExplicitlyAllowedPorts[]        = "explicitly-allowed-ports";