Remove TreatNullAs=NullString for HTMLTable*Element

http://whatwg.org/html#HTMLTableCaptionElement-partial
http://whatwg.org/html#htmltablecellelement
http://whatwg.org/html#HTMLTableCellElement-partial
http://whatwg.org/html#htmltableheadercellelement
http://whatwg.org/html#HTMLTableDataCellElement-partial
http://whatwg.org/html#HTMLTableColElement-partial
http://whatwg.org/html#HTMLTableElement-partial
http://whatwg.org/html#HTMLTableRowElement-partial
http://whatwg.org/html#HTMLTableSectionElement-partial

The spec has HTMLTableDataCellElement and HTMLTableHeaderCellElement
interfaces which we don't have yet, but ignore that here.

HTMLTable*Element.bgColor and HTMLTableElement.cellPadding/cellSpacing
have [TreatNullAs=EmptyString] in the spec.

HTMLTableCellElement.headers is a DOMSettableTokenList in the spec, so
leave it alone until that is fixed.

The tests for the updated properties pass in Firefox Nightly, IE11
Release Preview and Opera 12.16, with these exceptions:

IE throws an exception for the align/vAlign/frame/rules, and reflects
border/width/height as the empty string.

BUG=310298

Review URL: https://codereview.chromium.org/101493002

git-svn-id: svn://svn.chromium.org/blink/trunk@163081 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove TreatNullAs=NullString for HTMLHtmlElement

http://whatwg.org/html#HTMLHtmlElement-partial

The manifest attribute is not in the spec, so leave it alone pending a
decision about what to do with it:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/dSTAYLhhV3o/2Sh66-B7oAIJ

The test passes in Firefox Nightly, IE11 Release Preview and Opera 12.16.

BUG=310298

Review URL: https://codereview.chromium.org/101153003

git-svn-id: svn://svn.chromium.org/blink/trunk@163082 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove TreatNullAs=NullString for HTMLHeadingElement

http://whatwg.org/html#HTMLHeadingElement-partial

The updated test passes in Firefox Nightly and Opera 12.16,
but throws an exception in IE.

BUG=310298

Review URL: https://codereview.chromium.org/101193003

git-svn-id: svn://svn.chromium.org/blink/trunk@163083 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Little clean up GraphicsLayer.

1. Remove useless methods.
2. Remove useless null check.

Review URL: https://codereview.chromium.org/96103003

git-svn-id: svn://svn.chromium.org/blink/trunk@163084 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix test flakiness: http/tests/inspector/command-line-api-inspect.html

BUG=307294
R=pfeldman

Review URL: https://codereview.chromium.org/100613003

git-svn-id: svn://svn.chromium.org/blink/trunk@163085 bbb929c8-8fbe-4397-9dbb-9b2b20218538