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
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/Header.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/Header.java
index 282da08..424f3fa 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/Header.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/Header.java
@@ -250,11 +250,13 @@
       : Dispatcher.toSideBySide(base, patchSetId, info.path());
   }
 
-  private KeyCommand setupNav(InlineHyperlink link, int key, String help, FileInfo info) {
+  private KeyCommand 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)));
       KeyCommand k = new KeyCommand(0, key, help) {
         @Override
         public void onKeyPress(KeyPressEvent event) {
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.java
index 18a358a..a949c6b 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.java
@@ -22,4 +22,5 @@
   String expandBefore(int cnt);
   String expandAfter(int cnt);
   String draftSaved(Date when);
+  String fileNameWithShortcutKey(String file, String key);
 }
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.properties b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.properties
index 2d01e24..2ad8320 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.properties
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchMessages.properties
@@ -1,3 +1,4 @@
 expandBefore = +{0}⇧
 expandAfter = +{0}⇩
 draftSaved = Draft saved at {0,time,short}
+fileNameWithShortcutKey = {0} (Shortcut: {1})