Add enable-gamepad to content switches

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index e334f3c0b9387ff4050a50bb6ac7141c05c33852..385565457609e734c242379bbe45ee9aacb3062c 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -192,6 +192,9 @@ const char kEnableDeviceMotion[]            = "enable-device-motion";
 // Enable the JavaScript Full Screen API.
 const char kDisableFullScreen[]             = "disable-fullscreen";
 
+// Enable the Gamepad API
+const char kEnableGamepad[]                 = "enable-gamepad";
+
 // Enable the GPU plugin and Pepper 3D rendering.
 const char kEnableGPUPlugin[]               = "enable-gpu-plugin";