Support compiling templates in the browser.

extension/content_script.js

+// Copyright (c) 2012 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.
+
+// Glue code that runs on the page referencing dart web components.
+// Some logic has to be placed here rather than on the background page
+// because of chrome security restrictions.
+
+// Port used to send requests to the background page to proxy urls.
+var proxyPort = null;
+
+// Port used to send requests to the background page to parse components.
+var parsePort = null;
+
+function endsWith(str, pattern) {
+  return str.lastIndexOf(pattern) == str.length - pattern.length;
+}
+
+function onRequestParse() {
+  if (parsePort == null) {
+    parsePort = chrome.extension.connect({name: "parse"});
+  }
+  var l = window.location;
+  var pageUrl = l.protocol + "//" + l.host + l.pathname;
+  parsePort.postMessage({url: pageUrl});
+  parsePort.onMessage.addListener(function(msg) {
+    if (msg.type == "CREATE_DATA_URLS") {
+      var requests = msg.requests;
+      var response = [];
+      for (var i = 0; i < requests.length; i++) {
+        var request = requests[i];
+        var url = request.url;
+        var content = request.content;
+        var contentType =
+            endsWith(url, ".html") ? "text/html" : "application/javascript";
+        var objectUrl = webkitURL.createObjectURL(
+          new Blob([content], {type: contentType}));
+        response.push({url: url, redirectUrl: objectUrl});
+      }
+      if (proxyPort == null) {
+        proxyPort = chrome.extension.connect({name: "proxy"});
+      }
+      proxyPort.postMessage({requests: response});
+      // TODO(jacobr): remove timeout and listen for a message from the
+      // background page instead.
+      var generatedPageUrl = pageUrl.replace(/[/]([^/]+)$/,
+          function(match, p1) { return "/_" + p1 + ".html"});
+      window.setTimeout(function() {
+        for (var i = 0; i < requests.length; i++) {
+          var request = requests[i];
+          var url = request.url;
+          var content = request.content;
+          if (url == generatedPageUrl) {
+            // Replace the contents of the existing document with the
+            // proxied content at the url with an additional .html added.
+            // We prefer this versus redirecting to the page with an extra
+            // .html so that refreshing this page does the right thing.
+            var newDoc = document.open("text/html", "replace");
+            newDoc.write(content);
+            newDoc.close();
+          }
+        }
+      }, 100);
+    }
+  })
+
+}
+
+document.addEventListener("DOMContentLoaded", function() {
+  if (document.querySelector("link[rel=components], element, template")) {
+    // TODO(jacobr): should we always parse if there could be components?
+    onRequestParse();
+  }
+});
+
+window.addEventListener("message", function(event) {
+  if (event.source != window)
+    return;
+
+  if (event.data.type == "PARSE") {
+    onRequestParse();
+  }
+}, false);