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

chrome/renderer/renderer_main_platform_delegate_mac.mm

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/renderer_main_platform_delegate.h"
 
 #include "base/debug_util.h"
 
 #import <Foundation/Foundation.h>
 #import <ApplicationServices/ApplicationServices.h>
 extern "C" {
 #include <sandbox.h>
 }
 
 #include "base/sys_info.h"
 #include "chrome/common/chrome_switches.h"
 #include "third_party/WebKit/WebKit/mac/WebCoreSupport/WebSystemInterface.h"
 
 RendererMainPlatformDelegate::RendererMainPlatformDelegate(
     const MainFunctionParams& parameters)
         : parameters_(parameters) {
 }
 
 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();
 
   // Warmup CG - without these calls these two functions won't work in the
   // sandbox.
   CGColorSpaceRef rgb_colorspace =
       CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
 
   // Allocate a 1 byte image.
@@ skipping 51 matching lines @@
   if (error == -1) {
     LOG(ERROR) << "Failed to Initialize Sandbox: " << error_buff;
   }
   sandbox_free_error(error_buff);
   return success;
 }
 
 void RendererMainPlatformDelegate::RunSandboxTests() {
   // TODO(port): Run sandbox unit test here.
 }