diff --git a/tools/turbolizer/selection.js b/tools/turbolizer/selection.js
new file mode 100644
index 0000000..e9c02dd
--- /dev/null
+++ b/tools/turbolizer/selection.js
@@ -0,0 +1,107 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var Selection = function(handler) {
+  this.handler = handler;
+  this.selectionBase = null;
+  this.lastSelection = null;
+  this.selection = new Set();
+}
+
+
+Selection.prototype.isEmpty = function() {
+  return this.selection.size == 0;
+}
+
+
+Selection.prototype.clear = function() {
+  var handler = this.handler;
+  this.selectionBase = null;
+  this.lastSelection = null;
+  handler.select(this.selection, false);
+  handler.clear();
+  this.selection = new Set();
+}
+
+
+count = 0;
+
+Selection.prototype.select = function(s, isSelected) {
+  var handler = this.handler;
+  if (!(Symbol.iterator in Object(s))) { s = [s]; }
+  if (isSelected) {
+    let first = true;
+    for (let i of s) {
+      if (first) {
+        this.selectionBase = i;
+        this.lastSelection = i;
+        first = false;
+      }
+      this.selection.add(i);
+    }
+  } else {
+    let unselectSet = new Set();
+    for (let i of s) {
+      if (this.selection.has(i)) {
+        unselectSet.add(i);
+        this.selection.delete(i);
+      }
+    }
+  }
+  handler.select(this.selection, isSelected);
+}
+
+
+Selection.prototype.extendTo = function(pos) {
+  if (pos == this.lastSelection || this.lastSelection === null) return;
+
+  var handler = this.handler;
+  var pos_diff = handler.selectionDifference(pos, true, this.lastSelection, false);
+  var unselect_diff = [];
+  if (pos_diff.length == 0) {
+    pos_diff = handler.selectionDifference(this.selectionBase, false, pos, true);
+    if (pos_diff.length != 0) {
+      unselect_diff = handler.selectionDifference(this.lastSelection, true, this.selectionBase, false);
+      this.selection = new Set();
+      this.selection.add(this.selectionBase);
+      for (var d of pos_diff) {
+        this.selection.add(d);
+      }
+    } else {
+      unselect_diff = handler.selectionDifference(this.lastSelection, true, pos, false);
+      for (var d of unselect_diff) {
+        this.selection.delete(d);
+      }
+    }
+  } else {
+    unselect_diff = handler.selectionDifference(this.selectionBase, false, this.lastSelection, true);
+    if (unselect_diff != 0) {
+      pos_diff = handler.selectionDifference(pos, true, this.selectionBase, false);
+      if (pos_diff.length == 0) {
+        unselect_diff = handler.selectionDifference(pos, false, this.lastSelection, true);
+      }
+      for (var d of unselect_diff) {
+        this.selection.delete(d);
+      }
+    }
+    if (pos_diff.length != 0) {
+      for (var d of pos_diff) {
+        this.selection.add(d);
+      }
+    }
+  }
+  handler.select(unselect_diff, false);
+  handler.select(pos_diff, true);
+  this.lastSelection = pos;
+}
+
+
+Selection.prototype.detachSelection = function() {
+  var result = new Set();
+  for (var i of this.selection) {
+    result.add(i);
+  }
+  this.clear();
+  return result;
+}