SideBySide2: Show [ and ] shortcut keys in nav arrow tooltips

In the top right corner of a file the navigation cluster has a
tooltip on the up arrow but did not show the tooltip on the left
or right arrows. Show the key in the tooltip.

Change-Id: I192ef0ab8155c15b4bb35a18da33f74f15bb5537

gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/Header.java

@@ -178,11 +178,13 @@ class Header extends Composite {
     return p.toString();
   }
 
-  private void setupNav(InlineHyperlink link, int key, String help, FileInfo info) {
+  private void setupNav(InlineHyperlink link, char key, String help, FileInfo info) {
     if (info != null) {
       final String url = url(info);
       link.setTargetHistoryToken(url);
-      link.setTitle(FileInfo.getFileName(info.path()));
+      link.setTitle(PatchUtil.M.fileNameWithShortcutKey(
+          FileInfo.getFileName(info.path()),
+          Character.toString(key)));
       keys.add(new KeyCommand(0, key, help) {
         @Override
         public void onKeyPress(KeyPressEvent event) {

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.java

@@ -23,4 +23,5 @@ public interface PatchMessages extends Messages {
   String expandAfter(int cnt);
   String draftSaved(Date when);
   String patchSkipRegion(String lineNumber);
+  String fileNameWithShortcutKey(String file, String key);
 }

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.properties

@@ -2,3 +2,4 @@ expandBefore = +{0}⇧
 expandAfter = +{0}⇩
 draftSaved = Draft saved at {0,time,short}
 patchSkipRegion = ... skipped {0} common lines ...
+fileNameWithShortcutKey = {0} (Shortcut: {1})