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 #15474

Closes #15633

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`