[Prerender] Get the prerender mode from Finch field trial.

chrome/browser/chrome_browser_field_trials_mobile.h

Index: chrome/browser/chrome_browser_field_trials_mobile.h
diff --git a/chrome/browser/chrome_browser_field_trials_mobile.h b/chrome/browser/chrome_browser_field_trials_mobile.h
index 1e159673b5a6f0087940d0e25e0e13dec09869d9..941f9ce328fe5b5fd9ede1c9d0b323c1c2603ca9 100644
--- a/chrome/browser/chrome_browser_field_trials_mobile.h
+++ b/chrome/browser/chrome_browser_field_trials_mobile.h
@@ -5,19 +5,13 @@
 #ifndef CHROME_BROWSER_CHROME_BROWSER_FIELD_TRIALS_MOBILE_H_
 #define CHROME_BROWSER_CHROME_BROWSER_FIELD_TRIALS_MOBILE_H_
 
-#include "base/time/time.h"
-
-namespace base {
-class CommandLine;
-}
-
 namespace chrome {
 
 // Sets up mobile-only field trials.
 // Add an invocation of your field trial init function to this method, or to
 // SetupFieldTrials in chrome_browser_field_trials.cc if it is for all
 // platforms.
-void SetupMobileFieldTrials(const base::CommandLine& parsed_command_line);
+void SetupMobileFieldTrials();
 
 }  // namespace chrome