feat(plugins): add postResults hook for plugins

Allows plugins to include a postResults function, which will be called
after webdriver has been quit and the environment has been torn down.
This step may not modify the contents of the test results object.

lib/plugins.js

@@ -68,7 +68,7 @@ function pluginFunFactory(funName) {
           }
 
           // Output test results
-          if(pluginResult.specResults) {
+          if (pluginResult.specResults) {
             console.log('Plugin: ' + names[i] + ' (' + funName + ')');
             for (var j = 0; j < pluginResult.specResults.length; j++) {
               var specResult = pluginResult.specResults[j];
@@ -102,17 +102,28 @@ function pluginFunFactory(funName) {
 }
 
 /**
- *  Sets up plugins before tests are run.
- *  @return {q.Promise} A promise which resolves when the plugins have all been
- *    set up.
+ * Sets up plugins before tests are run.
+ *
+ * @return {q.Promise} A promise which resolves when the plugins have all been
+ *     set up.
  */
 Plugins.prototype.setup = pluginFunFactory('setup');
 
 /**
- *  Tears down plugins after tests are run.
- *  @return {q.Promise} A promise which resolves when the plugins have all been
- *    torn down.
+ * Tears down plugins after tests are run.
+ *
+ * @return {q.Promise} A promise which resolves when the plugins have all been
+ *     torn down.
  */
 Plugins.prototype.teardown = pluginFunFactory('teardown');
 
+/**
+ * Run after the test results have been processed (any values returned will
+ * be ignored), but before the process exits. Final chance for cleanup.
+ *
+ * @return {q.Promise} A promise which resolves when the plugins have all been
+ *     torn down.
+ */
+Plugins.prototype.postResults = pluginFunFactory('postResults');
+
 module.exports = Plugins;

lib/runner.js

@@ -316,7 +316,10 @@ Runner.prototype.run = function() {
     } else {
       return self.driverprovider_.teardownEnv();
     }
-  // 7) Exit process
+  // 7) Let plugins do final cleanup
+  }).then(function() {
+    return plugins.postResults();
+  // 8) Exit process
   }).then(function() {
     var exitCode = testPassed ? 0 : 1;
     return self.exit_(exitCode);