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

chrome/browser/renderer_host/render_sandbox_host_linux.cc

Index: chrome/browser/renderer_host/render_sandbox_host_linux.cc
diff --git a/chrome/browser/renderer_host/render_sandbox_host_linux.cc b/chrome/browser/renderer_host/render_sandbox_host_linux.cc
index 92105b441447df7b12ff50abf6e3f9a2a874a14a..29b84e9b2dcf9e7f8fd1140ac7da4eeb152b647a 100644
--- a/chrome/browser/renderer_host/render_sandbox_host_linux.cc
+++ b/chrome/browser/renderer_host/render_sandbox_host_linux.cc
@@ -643,6 +643,11 @@ RenderSandboxHostLinux::RenderSandboxHostLinux()
       pid_(0) {
 }
 
+// static
+RenderSandboxHostLinux* RenderSandboxHostLinux::GetInstance() {
+  return Singleton<RenderSandboxHostLinux>::get();
+}
+
 void RenderSandboxHostLinux::Init(const std::string& sandbox_path) {
   DCHECK(!initialized_);
   initialized_ = true;