Settings Router: Restrict navigateToPreviousRoute from going deeper.

Previous routes must now have equal or lesser depth.

BUG=640323
R=michaelpg@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2271003003
Cr-Commit-Position: refs/heads/master@{#414181}

chrome/browser/resources/settings/route.js

@@ -317,18 +317,19 @@ cr.define('settings', function() {
   };
 
   /**
-   * Navigates to the previous route, but will never exit Settings. If there is
-   * no previous route in the history, navigates to the immediate parent.
+   * Navigates to the previous route if it has an equal or lesser depth.
+   * If there is no previous route in history meeting those requirements,
+   * this navigates to the immediate parent. This will never exit Settings.
    */
   var navigateToPreviousRoute = function() {
     var previousRoute =
         window.history.state &&
         assert(getRouteForPath(/** @type {string} */ (window.history.state)));
 
-    if (previousRoute)
+    if (previousRoute && previousRoute.depth <= currentRoute_.depth)
       window.history.back();
     else
-      navigateTo(settings.getCurrentRoute().parent || Route.BASIC);
+      navigateTo(currentRoute_.parent || Route.BASIC);
   };
 
   window.addEventListener('popstate', function(event) {

chrome/test/data/webui/settings/route_tests.js

@@ -54,4 +54,71 @@ suite('route', function() {
       paths.add(route.path);
     });
   });
+
+  /**
+   * Tests a specific navigation situation.
+   * @param {!settings.Route} previousRoute
+   * @param {!settings.Route} currentRoute
+   * @param {!settings.Route} expectedNavigatePreviousResult
+   * @return {!Promise}
+   */
+  function testNavigateBackUsesHistory(previousRoute, currentRoute,
+                                       expectedNavigatePreviousResult) {
+    /**
+     * Returns a new promise that resolves after a window 'popstate' event.
+     * @return {!Promise}
+     */
+    function whenPopState() {
+      return new Promise(function(resolve) {
+        window.addEventListener('popstate', function callback() {
+          window.removeEventListener('popstate', callback);
+          resolve();
+        });
+      });
+    }
+
+    settings.navigateTo(previousRoute);
+    settings.navigateTo(currentRoute);
+    settings.navigateToPreviousRoute();
+
+    return whenPopState().then(function() {
+      assertEquals(expectedNavigatePreviousResult,
+                   settings.getCurrentRoute());
+    });
+  };
+
+  test('navigate back to parent previous route', function() {
+    return testNavigateBackUsesHistory(
+        settings.Route.BASIC,
+        settings.Route.PEOPLE,
+        settings.Route.BASIC);
+  });
+
+  test('navigate back to non-ancestor shallower route', function() {
+    return testNavigateBackUsesHistory(
+        settings.Route.ADVANCED,
+        settings.Route.PEOPLE,
+        settings.Route.ADVANCED);
+  });
+
+  test('navigate back to sibling route', function() {
+    return testNavigateBackUsesHistory(
+        settings.Route.APPEARANCE,
+        settings.Route.PEOPLE,
+        settings.Route.APPEARANCE);
+  });
+
+  test('navigate back to parent when previous route is deeper', function() {
+    settings.navigateTo(settings.Route.SYNC);
+    settings.navigateTo(settings.Route.PEOPLE);
+    settings.navigateToPreviousRoute();
+    assertEquals(settings.Route.BASIC, settings.getCurrentRoute());
+  });
+
+  test('navigate back to BASIC when going back from root pages', function() {
+    settings.navigateTo(settings.Route.PEOPLE);
+    settings.navigateTo(settings.Route.ADVANCED);
+    settings.navigateToPreviousRoute();
+    assertEquals(settings.Route.BASIC, settings.getCurrentRoute());
+  });
 });