RFR: JDK-8241190 Fix name clash for constants-summary CSS class

Wed Mar 18 22:54:49 UTC 2020

Please review a reasonably simple update to fix a recently discovered 
clash between two different uses of the same CSS class name.

Rather than do the absolute minimum fix and just change the affected 
class, I've changed the name of the class for all <body> elements by 
appending "-page".  In addition, I've declared new members in HtmlStyle 
and changed the code to always use those styles, to be more type-safe. 
And finally, as a sign of future intent, I've documented the new 
members.  Going forward, I can imagine a utility to generate a Markdown 
page providing an index of CSS class names and their description.

The test for these names is updated and marked with the bug number; one 
other test is affected.

-- Jon

JBS: https://bugs.openjdk.java.net/browse/JDK-8241190
Webrev: http://cr.openjdk.java.net/~jjg/8241190/webrev.00/