fix($sniffer): allow history for NW.js apps

Previously `$sniffer` incorrectly detected NW.js apps as Chrome Packaged Apps,
disallowing them to use the history API.

This commit correctly detects NW.js apps and allows them to use the History API.

Fixes angular#15474

Closes angular#15633

Author: frederikprijck

src/ng/sniffer.js

@@ -25,7 +25,10 @@ function $SnifferProvider() {
         // (see https://developer.chrome.com/apps/api_index). If sandboxed, they can be detected by
         // the presence of an extension runtime ID and the absence of other Chrome runtime APIs
         // (see https://developer.chrome.com/apps/manifest/sandbox).
+        // (NW.js apps have access to Chrome APIs, but do support `history`.)
+        isNw = $window.nw && $window.nw.process,
         isChromePackagedApp =
+            !isNw &&
             $window.chrome &&
             ($window.chrome.app && $window.chrome.app.runtime ||
                 !$window.chrome.app && $window.chrome.runtime && $window.chrome.runtime.id),

test/ng/snifferSpec.js

@@ -45,6 +45,25 @@ describe('$sniffer', function() {
     });
 
 
+    it('should be true on NW.js apps (which look similar to Chrome Packaged Apps)', function() {
+      var mockWindow = {
+        history: {
+          pushState: noop
+        },
+        chrome: {
+          app: {
+            runtime: {}
+          }
+        },
+        nw: {
+          process: {}
+        }
+      };
+
+      expect(sniffer(mockWindow).history).toBe(true);
+    });
+
+
     it('should be false on Chrome Packaged Apps', function() {
       // Chrome Packaged Apps are not allowed to access `window.history.pushState`.
       // In Chrome, `window.app` might be available in "normal" webpages, but `window.app.runtime`