Move 'title' attribute of NavMenu toggles to the <a> elements

Currently, the 'title' attribute on a NavMenu section/item is placed on the
top-level wrapper <div> element, instead of the dropdown-toggle's <a>
element.  Everywhere else, 'title' attributes are placed directly on the
<a> element of the button/item/link.

Since the top-level wrapper <div> encompasses the menu as well as the toggle,
any items in the menu that do not have their own explicit 'title' attribute
will inherit the top-level title.  In other words, menu items that should
not have tooltips will get the same tooltip as the dropdown-toggle.

This commit moves the 'title' attribute in NavMenu off the top-level <div>
and onto the toggle <a> element.

src/Components/NavMenu.php

@@ -155,12 +155,12 @@ protected function buildDropdownMenuStub( $menuDescription ) {
 		return $this->indent() . \Html::rawElement( 'div',
 				[
 					'class' => 'nav-item ' . $menuId . '-dropdown',
-					'title' => Linker::titleAttrib( $menuId )
 				],
 				\Html::rawElement( 'a',
 					[
 						'href' => '#',
 						'class' => 'nav-link ' . $menuId . '-toggle',
+						'title' => Linker::titleAttrib( $menuId ),
 					],
 					htmlspecialchars( $menuDescription['header'] ) )
 			);
@@ -179,7 +179,6 @@ protected function buildDropdownOpeningTags( $menuDescription ) {
 		$ret = $this->indent() . \Html::openElement( 'div',
 				[
 					'class' => 'nav-item dropdown ' . $menuId . '-dropdown',
-					'title' => Linker::titleAttrib( $menuId ),
 				] );
 
 		// add the dropdown toggle
@@ -190,6 +189,7 @@ protected function buildDropdownOpeningTags( $menuDescription ) {
 					'class' => 'nav-link dropdown-toggle ' . $menuId . '-toggle',
 					'data-toggle' => 'dropdown',
 					'data-boundary' => 'viewport',
+					'title' => Linker::titleAttrib( $menuId ),
 				],
 				htmlspecialchars( $menuDescription['header'] ) );