Add empty implementation of ThreadedInputConnection.deleteSurroundingTextInCodePoints().

This is needed to allow building with the N preview SDK.

BUG=595525,595522

Review URL: https://codereview.chromium.org/1808073002

Cr-Commit-Position: refs/heads/master@{#381652}

content/public/android/java/src/org/chromium/content/browser/input/ThreadedInputConnection.java

@@ -397,6 +397,14 @@ public class ThreadedInputConnection implements ChromiumBaseInputConnection {
         return true;
     }
 
+    /**
+     * @see InputConnection#deleteSurroundingTextInCodePoints(int, int)
+     */
+    public boolean deleteSurroundingTextInCodePoints(int beforeLength, int afterLength) {
+        // TODO(changwan): Implement this. http://crbug.com/595525
+        return false;
+    }
+
     /**
      * @see InputConnection#sendKeyEvent(android.view.KeyEvent)
      */