[Chromedriver] Add Device Metrics override support to ChromeDriver via Capabilities

chrome/test/chromedriver/chrome/chrome.h

Index: chrome/test/chromedriver/chrome/chrome.h
diff --git a/chrome/test/chromedriver/chrome/chrome.h b/chrome/test/chromedriver/chrome/chrome.h
index 56885bcfb77c67a824a2053c1580e797f960e89a..277c58d729ef3f6f0795350736400771f109a04c 100644
--- a/chrome/test/chromedriver/chrome/chrome.h
+++ b/chrome/test/chromedriver/chrome/chrome.h
@@ -40,6 +40,9 @@ class Chrome {
   // Get the operation system where Chrome is running.
   virtual std::string GetOperatingSystemName() = 0;
 
+  // Return whether the mobileEmulation capability has been enabled.
+  virtual bool IsMobileEmulationEnabled() const = 0;
+
   // Quits Chrome.
   virtual Status Quit() = 0;
 };