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..bf245f6fa675f6fb367d3f122f8fd613b1bb8c77 100644
--- a/chrome/browser/renderer_host/render_sandbox_host_linux.h
+++ b/chrome/browser/renderer_host/render_sandbox_host_linux.h
@@ -17,6 +17,9 @@
 // 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 {