Use a valid /prefetch argument when launching a process.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 905e42d23775469d062fe34c7770766548ee7fa6..040c5abe891b3e51a0b6c177dc3f66314999994f 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1322,6 +1322,11 @@ void RenderProcessHostImpl::AppendRendererCommandLine(
   command_line->AppendSwitchASCII(switches::kProcessType,
                                   switches::kRendererProcess);
 
+#if defined(OS_WIN)
+  if (GetContentClient()->browser()->ShouldUseWindowsPrefetchArgument())
+    command_line->AppendArg(switches::kPrefetchArgumentRenderer);
+#endif  // defined(OS_WIN)
+
   // Now send any options from our own command line we want to propagate.
   const base::CommandLine& browser_command_line =
       *base::CommandLine::ForCurrentProcess();