Add a new GetInstance() method for singleton classes used in chrome/browser files.

chrome/browser/dom_ui/history2_ui.cc

Index: chrome/browser/dom_ui/history2_ui.cc
diff --git a/chrome/browser/dom_ui/history2_ui.cc b/chrome/browser/dom_ui/history2_ui.cc
index 4f6867b52730286dc2606dc3d27162ddc2554dfb..3e9f67e2959205e30f1652cbc43c771b340430a9 100644
--- a/chrome/browser/dom_ui/history2_ui.cc
+++ b/chrome/browser/dom_ui/history2_ui.cc
@@ -126,7 +126,7 @@ DOMMessageHandler* BrowsingHistoryHandler2::Attach(DOMUI* dom_ui) {
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       NewRunnableMethod(
-          Singleton<ChromeURLDataManager>::get(),
+          ChromeURLDataManager::GetInstance(),
           &ChromeURLDataManager::AddDataSource,
           make_scoped_refptr(new DOMUIFavIconSource(dom_ui->GetProfile()))));
 
@@ -398,7 +398,7 @@ HistoryUI2::HistoryUI2(TabContents* contents) : DOMUI(contents) {
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       NewRunnableMethod(
-          Singleton<ChromeURLDataManager>::get(),
+          ChromeURLDataManager::GetInstance(),
           &ChromeURLDataManager::AddDataSource,
           make_scoped_refptr(html_source)));
 }