Start displaying comments and drafts.

Added drafts() call to CommentApi.

Added CommentBox for displaying comments.

Modified CodeMirrorDemo:
1. Implemented the algorithm and data structure that, given a line
number on one CM, return the corresponding line number on the other.
2. Added methods to display comments.

Modified some CSS styles for DiffTable.

Added wrapper for LineWidget in case we need it.

Change-Id: I9b9f6940ffa4eb1f87f79d5a655edd6beaab3b37

gerrit-gwtui/src/test/java/com/google/gerrit/client/diff/LineMapperTest.java

@@ -0,0 +1,91 @@
+// Copyright (C) 2013 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.client.diff;
+
+import static org.junit.Assert.assertEquals;
+
+import com.google.gerrit.common.changes.Side;
+
+import org.junit.Test;
+
+/** Unit tests for LineMapper */
+public class LineMapperTest {
+
+  @Test
+  public void testAppendCommon() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendCommon(10);
+    assertEquals(10, mapper.getLineA());
+    assertEquals(10, mapper.getLineB());
+  }
+
+  @Test
+  public void testAppendInsert() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendInsert(10);
+    assertEquals(0, mapper.getLineA());
+    assertEquals(10, mapper.getLineB());
+  }
+
+  @Test
+  public void testAppendDelete() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendDelete(10);
+    assertEquals(10, mapper.getLineA());
+    assertEquals(0, mapper.getLineB());
+  }
+
+  @Test
+  public void testFindInCommon() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendCommon(10);
+    assertEquals(9, mapper.lineOnOther(Side.PARENT, 9));
+  }
+
+  @Test
+  public void testFindAfterCommon() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendCommon(10);
+    assertEquals(10, mapper.lineOnOther(Side.PARENT, 10));
+  }
+
+  @Test
+  public void testFindInInsertGap() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendInsert(10);
+    assertEquals(-1, mapper.lineOnOther(Side.REVISION, 9));
+  }
+
+  @Test
+  public void testFindAfterInsertGap() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendInsert(10);
+    assertEquals(0, mapper.lineOnOther(Side.REVISION, 10));
+  }
+
+  @Test
+  public void testFindInDeleteGap() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendDelete(10);
+    assertEquals(-1, mapper.lineOnOther(Side.PARENT, 9));
+  }
+
+  @Test
+  public void testFindAfterDeleteGap() {
+    LineMapper mapper = new LineMapper();
+    mapper.appendDelete(10);
+    assertEquals(0, mapper.lineOnOther(Side.PARENT, 10));
+  }
+}