Get rid of --start-renderers-manually since it's been broken for a long time ...

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
===================================================================
--- chrome/common/pref_names.cc	(revision 11366)
+++ chrome/common/pref_names.cc	(working copy)
@@ -381,9 +381,6 @@
 const wchar_t kUninstallLastObservedRunTimeSec[] =
     L"uninstall_metrics.last_observed_running_time_sec";
 
-// If true, the user will be prompted to manually launch renderer processes.
-const wchar_t kStartRenderersManually[] = L"renderer.start_manually";
-
 // A collection of position, size, and other data relating to the browser
 // window to restore on startup.
 const wchar_t kBrowserWindowPlacement[] = L"browser.window_placement";