chore: add dartdoc compliance checks to build

Closes #3582

tools/build/dartapidocs.js

@@ -0,0 +1,44 @@
+var Q = require('q');
+var readline = require('readline');
+var spawn = require('child_process').spawn;
+var util = require('./util');
+
+module.exports = function(gulp, plugins, config) {
+  return function() {
+    return util.forEachSubDirSequential(config.dest, function(dir) {
+      var defer = Q.defer();
+      var done = defer.makeNodeResolver();
+
+      var supportedModules = [
+        'dist/dart/angular2',
+        // TODO: blocked by https://github.com/angular/angular/issues/3518
+        // 'dist/dart/angular2_material',
+        'dist/dart/benchpress'
+      ];
+
+      if (supportedModules.indexOf(dir) === -1) {
+        done();
+      } else {
+        console.log('INFO: running dartdocgen for ', dir);
+
+        var stream = spawn(config.command, ['.'], {
+          stdio: [process.stdin, process.stdout, process.stderr],
+          cwd: dir
+        });
+
+        stream.on('exit', function(code) {
+          if (code !== 0) {
+            done('ERROR: dartdocgen exited with non-zero status ' + code);
+          } else {
+            done();
+          }
+        });
+
+        stream.on('error', function(e) {
+          done('ERROR: dartdocgen reported error: ' + e);
+        });
+      }
+      return defer.promise;
+    });
+  };
+};