feat(build): Use broccoli for ts2dart transpilation.

Brocfile-dart.js

@@ -0,0 +1,43 @@
+// Brocfile to transpile sources from TypeScript to Dart using ts2dart.
+var Funnel = require('broccoli-funnel');
+var stew = require('broccoli-stew');
+var ts2dart = require('./dist/broccoli/broccoli-ts2dart');
+var path = require('path');
+
+// Transpile everything in 'modules'...
+var modulesTree = new Funnel('modules', {
+  include: ['**/*.js', '**/*.ts', '**/*.dart'], // .dart file available means don't translate.
+  exclude: ['rtts_assert/**/*'],  // ... except for the rtts_asserts (don't apply to Dart).
+  destDir: '/',  // Remove the 'modules' prefix.
+});
+
+// Transpile to dart.
+var dartTree = ts2dart.transpile(modulesTree);
+
+// Move around files to match Dart's layout expectations.
+dartTree = stew.rename(dartTree, function(relativePath) {
+  // If a file matches the `pattern`, insert the given `insertion` as the second path part.
+  var replacements = [
+    {pattern: /^benchmarks\/test\//, insertion: ''},
+    {pattern: /^benchmarks\//, insertion: 'web'},
+    {pattern: /^benchmarks_external\/test\//, insertion: ''},
+    {pattern: /^benchmarks_external\//, insertion: 'web'},
+    {pattern: /^example.?\//, insertion: 'web/'},
+    {pattern: /^example.?\/test\//, insertion: ''},
+    {pattern: /^[^\/]*\/test\//, insertion: ''},
+    {pattern: /^./, insertion: 'lib'},  // catch all.
+  ];
+
+  for (var i = 0; i < replacements.length; i++) {
+    var repl = replacements[i];
+    if (relativePath.match(repl.pattern)) {
+      var parts = relativePath.split('/');
+      parts.splice(1, 0, repl.insertion);
+      return path.join.apply(path, parts);
+    }
+  }
+  throw new Error('Failed to match any path', relativePath);
+});
+
+// Move the tree under the 'dart' folder.
+module.exports = stew.mv(dartTree, 'dart');