Build shadow_dom package in dart/pkg

pkg/shadow_dom/lib/src/platform/patches-shadow-css.js

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+(function(scope) {
+  // TODO(terry): Remove shimShadowDOMStyling2 until wrap/unwrap from a
+  //              dart:html Element to a JS DOM node is available.
+  /**
+   * Given the content of a STYLE tag and the name of a component shim the CSS
+   * and return the new scoped CSS to replace the STYLE's content.  The content
+   * is replaced in Dart's implementation of PolymerElement.
+   */
+  function shimShadowDOMStyling2(styleContent, name) {
+    if (window.ShadowDOMPolyfill) {
+      var content = this.convertPolyfillDirectives(styleContent, name);
+
+      // applyShimming calls shimAtHost and shipScoping
+      // shimAtHost code:
+      var r = '', l=0, matches;

[Jennifer Messerly, 2013/08/15 21:01:37]

spaces before and after equal sign?

+      while (matches = hostRuleRe.exec(content)) {
+        r += content.substring(l, matches.index);
+        r += this.scopeHostCss(matches[1], name);
+        l = hostRuleRe.lastIndex;
+      }
+      r += content.substring(l, content.length);
+      var re = new RegExp('^' + name + selectorReSuffix, 'm');
+      var atHostCssText = rulesToCss(this.findAtHostRules(cssToRules(r), re));
+
+      // shimScoping code:
+      // strip comments for easier processing
+      content = content.replace(cssCommentRe, '');
+
+      content = this.convertPseudos(content);
+      var rules = cssToRules(content);
+      var cssText = this.scopeRules(rules, name);
+
+      return atHostCssText + cssText;
+    }
+  }
+
+  // Minimal copied code from ShadowCSS, that is not exposed in
+  // PlatForm.ShadowCSS (local code).
+  var hostRuleRe = /@host[^{]*{(([^}]*?{[^{]*?}[\s\S]*?)+)}/gim,
+    cssCommentRe = /\/\*[^*]*\*+([^/*][^*]*\*+)*\//gim,
+    selectorReSuffix = '([>\\s~+\[.,{:][\\s\\S]*)?$';
+
+  function cssToRules(cssText) {
+    var style = document.createElement('style');
+    style.textContent = cssText;
+    document.head.appendChild(style);

[Jennifer Messerly, 2013/08/15 21:01:37]

dumb question, but is the appendChild really necessary?

I worry that adding+removing a style node to the document head could cause a lot
of style recalc. Is there a way we can avoid that (maybe append the node to an
iframe or something?)

+    var rules = style.sheet.cssRules;
+    style.parentNode.removeChild(style);
+    return rules;
+  }
+
+  function rulesToCss(cssRules) {
+    for (var i=0, css=[]; i < cssRules.length; i++) {

[Jennifer Messerly, 2013/08/15 21:01:37]

spaces

+      css.push(cssRules[i].cssText);
+    }
+    return css.join('\n\n');
+  }
+
+  // exports
+  scope.ShadowCSS.shimShadowDOMStyling2 = shimShadowDOMStyling2;
+})(window.Platform);