Add keyboard shortcuts and VIM bindings

Added global keyboard shortcuts.

Added shortcuts for:
- Opening / closing comment boxes.
- Saving drafts.
- Going up to change.

Included CodeMirror's VIM bindings for navigation. Removed the ones
that trigger insert mode. We probably need a way to include only a
subset of VIM bindings.

Fixed CodeMirror.on(). Added EventHandler for handling more types of
events.

Removed hiddenSkipMap hack and imported CodeMirror's official fix.

Change-Id: I75923e20e27434ca95882e2d70d10346bdf2323c

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

@@ -27,14 +27,11 @@ import com.google.gwt.user.client.ui.HTMLPanel;
 
 import net.codemirror.lib.CodeMirror;
 import net.codemirror.lib.CodeMirror.LineClassWhere;
-import net.codemirror.lib.CodeMirror.LineHandle;
 import net.codemirror.lib.Configuration;
 import net.codemirror.lib.LineWidget;
 import net.codemirror.lib.TextMarker;
 import net.codemirror.lib.TextMarker.FromTo;
 
-import java.util.Map;
-
 /** The Widget that handles expanding of skipped lines */
 class SkipBar extends Composite {
   interface Binder extends UiBinder<HTMLPanel, SkipBar> {}
@@ -67,11 +64,9 @@ class SkipBar extends Composite {
   private SkipBar otherBar;
   private CodeMirror cm;
   private int numSkipLines;
-  private Map<LineHandle, Integer> hiddenSkipMap;
 
-  SkipBar(CodeMirror cm, Map<LineHandle, Integer> hiddenSkipMap) {
+  SkipBar(CodeMirror cm) {
     this.cm = cm;
-    this.hiddenSkipMap = hiddenSkipMap;
     skipNum = new Anchor(true);
     upArrow = new Anchor(true);
     downArrow = new Anchor(true);
@@ -123,10 +118,9 @@ class SkipBar extends Composite {
   }
 
   private void expandAll() {
-    hiddenSkipMap.remove(
-        cm.getLineHandle(marker.find().getTo().getLine()));
     clearMarkerAndWidget();
     removeFromParent();
+    cm.focus();
   }
 
   private void expandBefore() {
@@ -140,7 +134,7 @@ class SkipBar extends Composite {
     LineWidget newWidget = cm.addLineWidget(newStart, getElement(), config);
     setWidget(newWidget);
     updateSkipNum();
-    hiddenSkipMap.put(cm.getLineHandle(end), numSkipLines);
+    cm.focus();
   }
 
   private void expandAfter() {
@@ -152,8 +146,7 @@ class SkipBar extends Composite {
         CodeMirror.pos(newEnd),
         COLLAPSED);
     updateSkipNum();
-    hiddenSkipMap.remove(cm.getLineHandle(oldEnd));
-    hiddenSkipMap.put(cm.getLineHandle(newEnd), numSkipLines);
+    cm.focus();
   }
 
   @UiHandler("skipNum")