Clean up dns prefetch code, and also port it.

chrome/browser/browser_main.cc

Index: chrome/browser/browser_main.cc
diff --git a/chrome/browser/browser_main.cc b/chrome/browser/browser_main.cc
index e7cd0a1d0d0e0b6dbcda281d807009841c535844..b54df42b8159ce42e9047eab71dc1e9f615d1d03 100644
--- a/chrome/browser/browser_main.cc
+++ b/chrome/browser/browser_main.cc
@@ -30,6 +30,7 @@
 #include "chrome/browser/dom_ui/chrome_url_data_manager.h"
 #include "chrome/browser/first_run.h"
 #include "chrome/browser/metrics/metrics_service.h"
+#include "chrome/browser/net/dns_global.h"
 #include "chrome/browser/profile_manager.h"
 #include "chrome/browser/shell_integration.h"
 #include "chrome/common/chrome_constants.h"
@@ -70,7 +71,6 @@
 #include "chrome/browser/jankometer.h"
 #include "chrome/browser/metrics/user_metrics.h"
 #include "chrome/browser/process_singleton.h"
-#include "chrome/browser/net/dns_global.h"
 #include "chrome/browser/net/sdch_dictionary_fetcher.h"
 #include "chrome/browser/net/url_fixer_upper.h"
 #include "chrome/browser/plugin_service.h"
@@ -108,7 +108,7 @@ void WillTerminate();
 
 #if defined(OS_WIN) || defined(OS_LINUX)
 // Perform any platform-specific work that needs to be done before the main
-// message loop is created and initialized. 
+// message loop is created and initialized.
 void WillInitializeMainMessageLoop(const CommandLine & command_line) {
 }
 
@@ -442,12 +442,14 @@ int BrowserMain(const MainFunctionParams& parameters) {
 #if defined(OS_WIN)
   // Initialize Winsock.
   net::EnsureWinsockInit();
+#endif  // defined(OS_WIN)
 
   // Initialize the DNS prefetch system
   chrome_browser_net::DnsPrefetcherInit dns_prefetch_init(user_prefs);
   chrome_browser_net::DnsPrefetchHostNamesAtStartup(user_prefs, local_state);
   chrome_browser_net::RestoreSubresourceReferrers(local_state);
 
+#if defined(OS_WIN)
   // Init common control sex.
   INITCOMMONCONTROLSEX config;
   config.dwSize = sizeof(config);