Use a valid /prefetch argument when launching a process.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 014731559badacda22307328e48ce6064b88843e..918054ff88b76a37363536e7286dfac15e711500 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -1257,6 +1257,12 @@ const char kForceImmersive[]                = "force-immersive";
 // This flag is only relevant for Windows currently.
 const char kNoNetworkProfileWarning[]       = "no-network-profile-warning";
 
+// /prefetch:# arguments for the browser process launched in background mode and
+// for the watcher process. These constants must be different from the
+// kPrefetchArgument* constants defined in content_switches.cc.

[gab, 2016/01/29 19:39:28]

s/These constants must.../Use profiles 6 and 7 as documented on
kPrefetchArgument* in content_switches.cc./

[fdoray, 2016/02/01 13:28:26]

Done.

+const char kPrefetchArgumentBrowserBackground[] = "/prefetch:6";
+const char kPrefetchArgumentWatcher[] = "/prefetch:7";
+
 // For the DelegateExecute verb handler to launch Chrome in desktop mode on
 // Windows 8 and higher.  Used when relaunching metro Chrome.
 const char kForceDesktop[]                  = "force-desktop";