Remove BrowserSignin, as it's not used anywhere.

chrome/browser/profiles/profile.h

Index: chrome/browser/profiles/profile.h
diff --git a/chrome/browser/profiles/profile.h b/chrome/browser/profiles/profile.h
index a5ba58d20601c77b044075a3dc6687282c7c0d0d..357e5cadc24af5de19039b419ebe81641c9842e0 100644
--- a/chrome/browser/profiles/profile.h
+++ b/chrome/browser/profiles/profile.h
@@ -54,7 +54,6 @@ class SpeechRecognizer;
 
 class AutocompleteClassifier;
 class BookmarkModel;
-class BrowserSignin;
 class ChromeAppCacheService;
 class ChromeURLDataManager;
 class Extension;
@@ -358,9 +357,6 @@ class Profile : public content::BrowserContext {
   // by the profile.
   virtual fileapi::FileSystemContext* GetFileSystemContext() = 0;
 
-  // Returns the BrowserSignin object assigned to this profile.
-  virtual BrowserSignin* GetBrowserSignin() = 0;
-
   // Returns the request context used for extension-related requests.  This
   // is only used for a separate cookie store currently.
   virtual net::URLRequestContextGetter* GetRequestContextForExtensions() = 0;