Add a html-based visualizer for TurboFan graphs

tools/turbolizer/selection-broker.js

+// 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 SelectionBroker = function() {
+  this.brokers = [];
+  this.dispatching = false;
+  this.lastDispatchingHandler = null;
+};
+
+SelectionBroker.prototype.addSelectionHandler = function(handler) {
+  this.brokers.push(handler);
+}
+
+SelectionBroker.prototype.select = function(from, ranges, selected) {
+  if (!this.dispatching) {
+    this.lastDispatchingHandler = from;
+    try {
+      this.dispatching = true;
+      for (var b of this.brokers) {
+        if (b != from) {
+          b.brokeredSelect(ranges, selected);
+        }
+      }
+    }
+    finally {
+      this.dispatching = false;
+    }
+  }
+}
+
+SelectionBroker.prototype.clear = function(from) {
+  this.lastDispatchingHandler = null;
+  if (!this.dispatching) {
+    try {
+      this.dispatching = true;
+      this.brokers.forEach(function(b) {
+        if (b != from) {
+          b.brokeredClear();
+        }
+      });
+    } finally {
+      this.dispatching = false;
+    }
+  }
+}