shadow-dom: Clean up existing tests for shadow root's methods.

This change rewrites existing tests in test-010.html. The file name is renamed
to shadow-root-001.html to better reflect the test content.
Merge pull request #255 from yutak/shadow-dom/shadow-root-methods

shadow-dom: Clean up existing tests for shadow root's methods.
Added tests to @Ms2ger's html/semantics/interfaces.html

for the a, area, dialog, figcaption, summary and track elements.
Merge pull request #257 from zqzhang/submission/zqzhang/html-interfaces

Added tests for the a, area, dialog, figcaption, summary and track elements html/semantics/interfaces.html.