Revert "Remove webkit_glue::BuildUserAgent(), change the contract in webkit_glue"

chrome/browser/ui/browser_init.cc

Index: chrome/browser/ui/browser_init.cc
diff --git a/chrome/browser/ui/browser_init.cc b/chrome/browser/ui/browser_init.cc
index 850d389e96e7ff759ff4da8a3dad3d591d3a425c..62e3b795dfbb7d76d653289baa1a57bc7381423c 100644
--- a/chrome/browser/ui/browser_init.cc
+++ b/chrome/browser/ui/browser_init.cc
@@ -78,6 +78,7 @@
 #include "net/base/net_util.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
+#include "webkit/glue/webkit_glue.h"
 
 #if defined(OS_MACOSX)
 #include "base/mac/mac_util.h"
@@ -689,6 +690,11 @@ bool BrowserInit::LaunchWithProfile::Launch(
     }
   }
 
+  if (command_line_.HasSwitch(switches::kUserAgent)) {
+    webkit_glue::SetUserAgent(command_line_.GetSwitchValueASCII(
+        switches::kUserAgent));
+  }
+
   // Open the required browser windows and tabs. First, see if
   // we're being run as an application window. If so, the user
   // opened an app shortcut.  Don't restore tabs or open initial