[ChromeDriver] Support mobile emulation on desktop Chrome.

chrome/test/chromedriver/capabilities.h

Index: chrome/test/chromedriver/capabilities.h
diff --git a/chrome/test/chromedriver/capabilities.h b/chrome/test/chromedriver/capabilities.h
index 998c56aed19f08aa454700c9ea970ea90d1bbf32..c21c045e54bf5821644e2e0d7c34d589b59b3423 100644
--- a/chrome/test/chromedriver/capabilities.h
+++ b/chrome/test/chromedriver/capabilities.h
@@ -14,6 +14,7 @@
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
 #include "chrome/test/chromedriver/chrome/log.h"
 #include "chrome/test/chromedriver/net/net_util.h"
 
@@ -91,6 +92,9 @@ struct Capabilities {
   // ChromeDriver dies.
   bool detach;
 
+  // Device metrics for use in Device Emulation.
+  scoped_ptr<DeviceMetrics> device_metrics;
+
   // Set of switches which should be removed from default list when launching
   // Chrome.
   std::set<std::string> exclude_switches;