fix: Promise polyfill for zone

Fixes evaluateAsync behavior when [zone.js](https://github.com/angular/zone.js) has mucked with Promise.
Adds zone.js to the smoke tests so regression won't happen again.

Addresses #1177.

lighthouse-cli/test/fixtures/dobetterweb/dbw_tester.html

@@ -295,6 +295,6 @@ <h2>Do better web tester page</h2>
 }
 </script>
 
-<script src="/promise_polyfill.js"></script>
+<script src="/zone.js"></script>
 </body>
 </html>

lighthouse-cli/test/fixtures/static-server.js

@@ -27,11 +27,11 @@ function requestHandler(request, response) {
   const queryString = requestUrl.search;
   let absoluteFilePath = path.join(__dirname, filePath);
 
-  if (filePath === '/promise_polyfill.js') {
+  if (filePath === '/zone.js') {
     // evaluateAsync previously had a bug that LH would fail if a page polyfilled Promise.
-    // We bring in a third-party Promise polyfill to ensure we don't still fail.
+    // We bring in an aggressive Promise polyfill (zone) to ensure we don't still fail.
     const thirdPartyPath = '../../../lighthouse-core/third_party';
-    absoluteFilePath = path.join(__dirname, `${thirdPartyPath}/promise-polyfill/promise.js`);
+    absoluteFilePath = path.join(__dirname, `${thirdPartyPath}/zone/zone.js`);
   }
 
   fs.exists(absoluteFilePath, fsExistsCallback);

lighthouse-core/gather/driver.js

@@ -143,15 +143,19 @@ class Driver {
       );
 
       this.sendCommand('Runtime.evaluate', {
-        // We need to wrap the raw expression for several purposes
+        // We need to expliticly wrap the raw expression for several purposes:
         // 1. Ensure that the expression will be a native Promise and not a polyfill/non-Promise.
-        // 2. Ensure that errors captured in the Promise are converted into plain-old JS Objects
+        // 2. Ensure that errors in the expression are captured by the Promise.
+        // 3. Ensure that errors captured in the Promise are converted into plain-old JS Objects
         //    so that they can be serialized properly b/c JSON.stringify(new Error('foo')) === '{}'
         expression: `(function wrapInNativePromise() {
           const __nativePromise = window.__nativePromise || Promise;
-          return __nativePromise.resolve()
-            .then(_ => ${expression})
-            .catch(${wrapRuntimeEvalErrorInBrowser.toString()});
+          return new __nativePromise(function (resolve) {
+            return __nativePromise.resolve()
+              .then(_ => ${expression})
+              .catch(${wrapRuntimeEvalErrorInBrowser.toString()})
+              .then(resolve);
+          });
         }())`,
         includeCommandLineAPI: true,
         awaitPromise: true,