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

chrome/browser/renderer_host/render_sandbox_host_linux.h

Index: chrome/browser/renderer_host/render_sandbox_host_linux.h
diff --git a/chrome/browser/renderer_host/render_sandbox_host_linux.h b/chrome/browser/renderer_host/render_sandbox_host_linux.h
index b0122e892a14eed01ce652566d082785edb14450..2cb060434a7b927860ea7ee3574088d9dd79a93d 100644
--- a/chrome/browser/renderer_host/render_sandbox_host_linux.h
+++ b/chrome/browser/renderer_host/render_sandbox_host_linux.h
@@ -11,12 +11,16 @@
 #include <string>
 
 #include "base/logging.h"
-#include "base/singleton.h"
+
+template <typename T> struct DefaultSingletonTraits;
 
 // This is a singleton object which handles sandbox requests from the
 // renderers.
 class RenderSandboxHostLinux {
  public:
+  // Returns the singleton instance.
+  static RenderSandboxHostLinux* GetInstance();
+
   // Get the file descriptor which renderers should be given in order to signal
   // crashes to the browser.
   int GetRendererSocket() const {