Remove obsolete interface.

chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java b/chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java
index 640779a93e0a12a502b80c36e33f60437f9a4818..f2c56a11d8fc2f885cf2000ae7881daf1f4fb78b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java
@@ -114,13 +114,6 @@ public class SigninManager {
     }
 
     /**
-     * Same as SignInFlowObserver.
-     * TODO(newt): Remove this interface once all clients inherit from SignInFlowObserver.
-     */
-    public interface Observer extends SignInFlowObserver {
-    }
-
-    /**
      * A helper method for retrieving the application-wide SigninManager.
      * <p/>
      * Can only be accessed on the main thread.