Enable --single-process for Mac and Linux....

chrome/renderer/renderer_main_platform_delegate_mac.mm

Index: chrome/renderer/renderer_main_platform_delegate_mac.mm
===================================================================
--- chrome/renderer/renderer_main_platform_delegate_mac.mm	(revision 10220)
+++ chrome/renderer/renderer_main_platform_delegate_mac.mm	(working copy)
@@ -24,6 +24,9 @@
 RendererMainPlatformDelegate::~RendererMainPlatformDelegate() {
 }
 
+// TODO(mac-port): Any code needed to initialize a process for
+// purposes of running a renderer needs to also be reflected in
+// chrome_dll_main.cc for --single-process support.
 void RendererMainPlatformDelegate::PlatformInitialize() {
   // Load WebKit system interfaces.
   InitWebCoreSystemInterface();