Use a valid /prefetch argument when launching a process.

content/browser/gpu/gpu_process_host.cc

Index: content/browser/gpu/gpu_process_host.cc
diff --git a/content/browser/gpu/gpu_process_host.cc b/content/browser/gpu/gpu_process_host.cc
index 99270e53bd52ad3ec3c7e89479a01138b97089a5..cf814c8ad2ad580fe19030916f2d8422ea9b7b2e 100644
--- a/content/browser/gpu/gpu_process_host.cc
+++ b/content/browser/gpu/gpu_process_host.cc
@@ -996,6 +996,11 @@ bool GpuProcessHost::LaunchGpuProcess(const std::string& channel_id) {
   cmd_line->AppendSwitchASCII(switches::kProcessType, switches::kGpuProcess);
   cmd_line->AppendSwitchASCII(switches::kProcessChannelID, channel_id);
 
+#if defined(OS_WIN)
+  if (GetContentClient()->browser()->ShouldUseWindowsPrefetchArgument())
+    cmd_line->AppendArg(switches::kPrefetchArgumentGpu);
+#endif  // defined(OS_WIN)
+
   if (kind_ == GPU_PROCESS_KIND_UNSANDBOXED)
     cmd_line->AppendSwitch(switches::kDisableGpuSandbox);