Never launch a new window when --no-startup-window is specified.

BUG=455070
TEST=manual, according to steps in bug.

Review URL: https://codereview.chromium.org/893383002

Cr-Commit-Position: refs/heads/master@{#314603}

chrome/browser/ui/startup/startup_browser_creator.cc

@@ -600,6 +600,11 @@ bool StartupBrowserCreator::ProcessCmdLineImpl(
     silent_launch = true;
   }
 
+  // If --no-startup-window is specified and Chrome is already running then do
+  // not open a new window.
+  if (!process_startup && command_line.HasSwitch(switches::kNoStartupWindow))
+    silent_launch = true;
+
   // If we don't want to launch a new browser window or tab we are done here.
   if (silent_launch)
     return true;