Rename subdirectory names in LayoutTests/html/.

third_party/WebKit/LayoutTests/html/README.md

 # html
 
 This directory contains tests related to [HTML standard](https://html.spec.whatwg.org/).
 
 Please do not add tests unrelated to HTML standard.
 
 ## Exceptions
 
 Some areas have their own directories not under html/.
 
 *   Canvas: ../fast/canvas/ or ../canvas/
 *   Editing: ../editing/
 *   Forms: [../fast/forms/](../fast/forms/README.md)
 *   History API: ../fast/history/
 *   Media elements: ../media/
 *   Navigation/loading: ../fast/loader/, ../loader/, or ../http/tests/loading/
 
 
 ## Sub-directories
 
 *   details_summary/
 
     DETAILS and SUMMARY elements.
 
 *   dialog/
 
     DIALOG element.
 
-*   document-metadata/
+*   document_metadata/
 
     [Document metadata elements](https://html.spec.whatwg.org/multipage/semantics.html#document-metadata);
     HEAD, TITLE, BASE, LINK, META, and STYLE.
 
-*   grouping-content/
+*   grouping_content/
 
     [Grouping content elmeents](https://html.spec.whatwg.org/multipage/semantics.html#grouping-content);
     P, HR, PRE, BLOCKQUOTE, OL, UL, LI, DL, DT, DD, FIGURE, FIGCAPTION, MAIN,
     and DIV.
 
 *   marquee/
 
     MARQUEE element.
 
 *   menu_menuitem/
 
     MENU and MENUITEM elements.
 
 *   sections/
 
     [Sections elements](https://html.spec.whatwg.org/multipage/semantics.html#sections);
     BODY, ARTICLE, SECTION, NAV, ASIDE, Hn, HGROUP, HEADER, FOOTER, and ADDRESS.
 
-*   text-level-semantics/
+*   text_level_semantics/
 
     [Text-level semantics elements](https://html.spec.whatwg.org/multipage/semantics.html#text-level-semantics);
     A, EM, STRONG, SMALL, S, CITE, Q, DFN, ABBR, RUBY, RT, RP, DATA, TIME, CODE,
     VAR, SAMP, KBD, SUB, SUP, I, B, U, MARK, BDI, BDO, SPAN, BR, and WBR.