Create package for HTML imports

pkg/html_import/lib/src/boot.js

Index: pkg/html_import/lib/src/boot.js
diff --git a/pkg/html_import/lib/src/boot.js b/pkg/html_import/lib/src/boot.js
new file mode 100644
index 0000000000000000000000000000000000000000..3ec48971bfbe3ddc13cda2461cde490fdfbace30
--- /dev/null
+++ b/pkg/html_import/lib/src/boot.js
@@ -0,0 +1,37 @@
+/*
+ * Copyright 2013 The Polymer Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ */
+(function(){
+
+// bootstrap
+
+// IE shim for CustomEvent
+if (typeof window.CustomEvent !== 'function') {
+  window.CustomEvent = function(inType) {
+     var e = document.createEvent('HTMLEvents');
+     e.initEvent(inType, true, true);
+     return e;
+  };
+}
+
+function bootstrap() {
+  // preload document resource trees
+  HTMLImports.importer.load(document, function() {
+    HTMLImports.parser.parse(document);
+    HTMLImports.readyTime = new Date().getTime();
+    // send HTMLImportsLoaded when finished
+    document.dispatchEvent(
+      new CustomEvent('HTMLImportsLoaded', {bubbles: true})
+    );
+  });
+};
+
+if (document.readyState === 'complete') {
+  bootstrap();
+} else {
+  window.addEventListener('DOMContentLoaded', bootstrap);
+}
+
+})();