[proguard] Add VisibleToTesting to clearHistory on NavigationController.

content/public/android/java/src/org/chromium/content_public/browser/NavigationController.java

Index: content/public/android/java/src/org/chromium/content_public/browser/NavigationController.java
diff --git a/content/public/android/java/src/org/chromium/content_public/browser/NavigationController.java b/content/public/android/java/src/org/chromium/content_public/browser/NavigationController.java
index 3e9eb09c50d0bfa7e7c457b2ddcd19596396eb2d..d9c18690cb9d7a2eb9d74ddf54b2a01b278ffa06 100644
--- a/content/public/android/java/src/org/chromium/content_public/browser/NavigationController.java
+++ b/content/public/android/java/src/org/chromium/content_public/browser/NavigationController.java
@@ -4,6 +4,8 @@
 
 package org.chromium.content_public.browser;
 
+import org.chromium.base.VisibleForTesting;
+
 /**
  * The NavigationController Java wrapper to allow communicating with the native
  * NavigationController object.
@@ -90,6 +92,7 @@ public interface NavigationController {
      * Clears NavigationController's page history in both backwards and
      * forwards directions.
      */
+    @VisibleForTesting
     public void clearHistory();
 
     /**