Move --user-agent overriding logic from chrome into content.

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index 8d360c37ed1a76610e6a72a1f03cae845b914760..5d1cb6ea8b6e3f4ed4faabbab2786795a4a7eba2 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -223,9 +223,10 @@ int RunZygote(const content::MainFunctionParams& main_function_params,
   // If a custom user agent was passed on the command line, we need
   // to (re)set it now, rather than using the default one the zygote
   // initialized.
-  bool custom = false;
-  std::string ua = content::GetContentClient()->GetUserAgent(&custom);
-  if (custom) webkit_glue::SetUserAgent(ua, custom);
+  if (command_line.HasSwitch(switches::kUserAgent)) {
+    webkit_glue::SetUserAgent(
+        command_line.GetSwitchValueASCII(switches::kUserAgent), true);
+  }
 
   // The StatsTable must be initialized in each process; we already
   // initialized for the browser process, now we need to initialize
@@ -467,6 +468,15 @@ class ContentMainRunnerImpl : public content::ContentMainRunner {
     if (delegate)
       delegate->PreSandboxStartup();
 
+    // If a custom user agent was passed on the command line we need
+    // to set it now before webkit_glue::GetUserAgent() is called so that the
+    // UA doesn't change.
+    if (command_line.HasSwitch(switches::kUserAgent)) {
+      std::string ua = command_line.GetSwitchValueASCII(switches::kUserAgent);
+      webkit_glue::SetUserAgent(
+          command_line.GetSwitchValueASCII(switches::kUserAgent), true);
+    }
+
     if (!process_type.empty())
       CommonSubprocessInit(process_type);