Implement contextmenu attribute with basic support of <menu>

LayoutTests/fast/dom/HTMLElement/script-tests/contextmenu.js

+description('Tests the contextmenu attribute.');

[tkent, 2014/08/05 02:33:22]

Please do not make new script-test.  This file should be merged into
contextmenu.html.

+
+debug("Test with valid contextmenu attribute");
+document.write("<div id='container1' contextmenu='menu1'><menu id='menu1' type='popup' label='menu 1'></menu></div>");
+shouldBe("document.getElementById('container1').contextMenu.id", "'menu1'");
+shouldBe("document.getElementById('container1').contextMenu.type", "'popup'");
+shouldBe("document.getElementById('container1').contextMenu.label", "'menu 1'");
+
+debug("Test with invalid contextmenu attribute");
+document.write("<div id='container2' contextmenu='nonexistent_menu'><menu id='menu2' type='popup' label='menu 2'></menu></div>");
+shouldBe("document.getElementById('container2').contextMenu", "null");
+

[tkent, 2014/08/05 02:33:22]

Need a test for a case where an element without contextmenu attribute.

What should happen if the referred <menu> has no type=popup?  What does the
specification say about it?

+debug("Test setting contextmenu attribute");
+document.write("<div id='container3'></div>");
+var menu = document.createElement('menu');
+menu.id = 'menu3';
+menu.type = 'popup';
+menu.label = 'menu 3';
+document.getElementById('container3').appendChild(menu);
+var container3 = document.getElementById('container3');
+container3.contextMenu = menu;
+shouldBe("container3.contextMenu.id", "'menu3'");

[tkent, 2014/08/05 02:33:22]

Use shouldBeEqualToString().

+shouldBe("container3.contextMenu.type", "'popup'");
+shouldBe("container3.contextMenu.label", "'menu 3'");
+
+debug("Test setting contextmenu attribute with menu element without id");
+document.write("<div id='container4'></div>");
+var menu1 = document.createElement('menu');
+menu1.type = 'popup';
+menu1.label = 'menu 4';
+document.getElementById('container4').appendChild(menu1);
+var container4 = document.getElementById('container4');
+container4.contextMenu = menu1;
+shouldBe("container4.contextMenu", "null");

[tkent, 2014/08/05 02:33:22]

Use shouldBeNull().

+
+debug("Test setting contextmenu attribute with multiple menu element with same id");
+document.write("<div id='container5'></div>");
+var menu2 = document.createElement('menu');
+menu2.id = 'menu5';
+menu2.type = 'popup';
+menu2.label = 'menu 5';
+var menu3 = document.createElement('menu');
+menu3.id = 'menu5';
+menu3.type = 'popup';
+menu3.label = 'menu 6';
+document.getElementById('container5').appendChild(menu2);
+document.getElementById('container5').appendChild(menu3);
+var container5 = document.getElementById('container5');
+container5.contextMenu = menu2;

[tkent, 2014/08/05 02:33:22]

Set menu3 instead of menu2.  What should happen in such case?

+shouldBe("container5.contextMenu.id", "'menu5'");
+shouldBe("container5.contextMenu.type", "'popup'");
+shouldBe("container5.contextMenu.label", "'menu 5'");

[tkent, 2014/08/05 02:33:22]

What should happen if
 - element.contextMenu = null
 - element.contextMenu = "foobar"
 - element.contextMenu = document.createComment('foo')
 - element.contextMenu = menu-element-with-id-without-type
 - element.contextMenu = menu-element-with-id-in-ShadowRoot