DevTools: use diff_match_patch instead of jsdifflib for text diffing.

Source/devtools/front_end/diff/Diff.js

Index: Source/devtools/front_end/diff/Diff.js
diff --git a/Source/devtools/front_end/diff/Diff.js b/Source/devtools/front_end/diff/Diff.js
new file mode 100644
index 0000000000000000000000000000000000000000..9b844ad8b435192c4b3f78e686c85cf416e10328
--- /dev/null
+++ b/Source/devtools/front_end/diff/Diff.js
@@ -0,0 +1,56 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+WebInspector.Diff = {
+    /**
+     * @param {string} text1
+     * @param {string} text2
+     * @return {!Array.<!{0: number, 1: string}>}
+     */
+    charDiff: function(text1, text2)
+    {
+        var differ = new diff_match_patch();
+        return differ.diff_main(text1, text2);
+    },
+
+    /**
+     * @param {!Array.<string>} lines1
+     * @param {!Array.<string>} lines2
+     * @return {!Array.<!{0: number, 1: string}>}
+     */
+    lineDiff: function(lines1, lines2)
+    {
+        var lineToChar = new Map();
+        var charCode = 33;
+        var text1 = encode(lines1);
+        var text2 = encode(lines2);
+
+        return WebInspector.Diff.charDiff(text1, text2);
+
+        /**
+         * @param {!Array.<string>} lines
+         * @return {string}
+         */
+        function encode(lines)
+        {
+            var text = "";
+            for (var i = 0; i < lines.length; ++i) {
+                var line = lines[i];
+                var character = lineToChar.get(line);
+                if (!character) {
+                    character = String.fromCharCode(charCode++);
+                    lineToChar.set(line, character);
+                }
+                text += character;
+            }
+            return text;
+        }
+    },
+}
+
+WebInspector.Diff.Operation = {
+    Equal: 0,
+    Insert: 1,
+    Delete: -1
+}