Package protect ExternalNavigationDelegate.

This should not be used by anyone other that ExternalNavigationHandler.

Review URL: https://codereview.chromium.org/1091653002

Cr-Commit-Position: refs/heads/master@{#325350}

chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationDelegate.java

@@ -16,7 +16,7 @@ import java.util.List;
  * A delegate for the class responsible for navigating to external applications from Chrome. Used
  * by {@link ExternalNavigationHandler}.
  */
-public interface ExternalNavigationDelegate {
+interface ExternalNavigationDelegate {
     /**
      * Get the list of component name of activities which can resolve |intent|.
      */

chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationDelegateImpl.java

@@ -36,7 +36,7 @@ import java.util.List;
 /**
  * The main implementation of the {@link ExternalNavigationDelegate}.
  */
-public class ExternalNavigationDelegateImpl implements ExternalNavigationDelegate {
+class ExternalNavigationDelegateImpl implements ExternalNavigationDelegate {
     private static final String TAG = "ExternalNavigationDelegateImpl";
     private final Activity mActivity;