Minor refactor of diff code to prepare for unified view

Pulled some classes out of SideBySide2. There will be a lot of
common code between the upcoming Unified2 and SideBySide2.

Fixed a minor bug in skip line rendering. It was still relying
on Side.PARENT. Changed to use DisplaySide.A.

Deleted deprecated PatchSelectBox2.

Change-Id: I87d608d7e6a4330096d65b0fc1b99c1c5160d119

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

@@ -0,0 +1,57 @@
+// 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 com.google.gwt.core.client.JsArrayString;
+
+import net.codemirror.lib.LineCharacter;
+
+/** An iterator for intraline edits */
+class EditIterator {
+  private final JsArrayString lines;
+  private final int startLine;
+  private int currLineIndex;
+  private int currLineOffset;
+
+  EditIterator(JsArrayString lineArray, int start) {
+    lines = lineArray;
+    startLine = start;
+  }
+
+  LineCharacter advance(int numOfChar) {
+    while (currLineIndex < lines.length()) {
+      int lengthWithNewline =
+          lines.get(currLineIndex).length() - currLineOffset + 1;
+      if (numOfChar < lengthWithNewline) {
+        LineCharacter at = LineCharacter.create(
+            startLine + currLineIndex,
+            numOfChar + currLineOffset);
+        currLineOffset += numOfChar;
+        return at;
+      }
+      numOfChar -= lengthWithNewline;
+      advanceLine();
+      if (numOfChar == 0) {
+        return LineCharacter.create(startLine + currLineIndex, 0);
+      }
+    }
+    throw new IllegalStateException("EditIterator index out of bound");
+  }
+
+  private void advanceLine() {
+    currLineIndex++;
+    currLineOffset = 0;
+  }
+}