fix(nav-bar): improve focus behavior for click events (#11600)

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## PR Checklist
Please check that your PR fulfills the following requirements:
- [x] The commit message follows [our guidelines](https://github.com/angular/material/blob/master/.github/CONTRIBUTING.md#-commit-message-format)
- [x] Tests for the changes have been added or this is not a bug fix / enhancement
- [x] Docs have been added, updated, or were not required

## PR Type
What kind of change does this PR introduce?
<!-- Please check the one that applies to this PR using "x". -->
```
[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:
```

## What is the current behavior?
Clicking on nav items with a mouse causes the focus to move to the previously clicked nav item instead of the newly clicked nav item.
<!-- Please describe the current behavior that you are modifying and link to one or more relevant issues. -->
Issue Number: 
Fixes #11591. Relates to #11494. Closes #11598.

## What is the new behavior?
- Focus is moved to the new nav item after it is clicked.
- remove hover style that is inconsistent with spec
- add test from @codymikol 

## Does this PR introduce a breaking change?
```
[ ] Yes
[x] No
```
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## Other information
Thank you to @codymikol for doing the initial investigation into this regression!

src/components/navBar/navBar.js

@@ -114,10 +114,9 @@ function MdNavBar($mdAria, $mdTheming) {
 
 /**
  * Controller for the nav-bar component.
- *
- * TODO update this with a link to tablist when that implementation gets merged.
- * Accessibility functionality is implemented as a site navigator with a listbox, according to
- * https://www.w3.org/TR/wai-aria-practices/#Site_Navigator_Tabbed_Style.
+ * Accessibility functionality is implemented as a tablist
+ * (https://www.w3.org/TR/wai-aria-1.0/complete#tablist) and
+ * tabs (https://www.w3.org/TR/wai-aria-1.0/complete#tab).
  *
  * @param {!angular.JQLite} $element
  * @param {!angular.Scope} $scope
@@ -196,6 +195,7 @@ MdNavBarController.prototype._initTabs = function() {
 MdNavBarController.prototype._updateTabs = function(newValue, oldValue) {
   var self = this;
   var tabs = this._getTabs();
+  var sameTab = newValue === oldValue;
 
   // this._getTabs can return null if nav-bar has not yet been initialized
   if (!tabs) return;
@@ -217,6 +217,11 @@ MdNavBarController.prototype._updateTabs = function(newValue, oldValue) {
 
   this._$timeout(function() {
     self._updateInkBarStyles(newTab, newIndex, oldIndex);
+    // Don't change focus when there is no newTab, the new and old tabs are the same, or when
+    // called from MdNavBarController._initTabs() which would have no oldTab defined.
+    if (newTab && oldTab && !sameTab) {
+      self._moveFocus(oldTab, newTab);
+    }
   });
 };
 
@@ -596,6 +601,9 @@ function MdNavItem($mdAria, $$rAF, $mdUtil, $window) {
         });
 
         navButton.on('click', function() {
+          // This triggers a watcher on mdNavBar.mdSelectedNavItem which calls
+          // MdNavBarController._updateTabs() after a $timeout. That function calls
+          // MdNavItemController.setSelected() for the old tab with false and the new tab with true.
           mdNavBar.mdSelectedNavItem = mdNavItem.name;
           scope.$apply();
         });

src/components/navBar/navBar.scss

@@ -34,11 +34,6 @@ $md-nav-bar-height: 48px;
   &:focus {
     outline: none;
   }
-
-  &:hover {
-    background-color: inherit;
-  }
-
 }
 
 md-nav-ink-bar {

src/components/navBar/navBar.spec.js

@@ -183,6 +183,17 @@ describe('mdNavBar', function() {
       expect($scope.selectedTabRoute).toBe('tab2');
     });
 
+    it('should add the md-focused class when focused', function () {
+      $scope.selectedTabRoute = 'tab1';
+      createTabs();
+      var tab2Ctrl = getTabCtrl('tab2');
+      angular.element(tab2Ctrl.getButtonEl()).triggerHandler('focus');
+      angular.element(tab2Ctrl.getButtonEl()).triggerHandler('click');
+      $scope.$apply();
+      $timeout.flush();
+      expect(tab2Ctrl.getButtonEl().classList.contains('md-focused')).toBe(true);
+    });
+
     it('adds ui-sref-opts attribute to nav item when sref-opts attribute is ' +
         'defined', function() {
           create(