Break the StyleResolverUpdateFlag enum into StyleResolverUpdateType and StyleResolverUpdateMode

Before this patch the StyleResolverUpdateFlag served multiple purposes which is very confusing.

Now there's two enums:

StyleResolverUpdateType: This is if the StyleResolver update should be async or deferred.
StyleResolverUpdateMode: This is if we should attempt to use the StyleInvalidationAnalysis.

This change was a part of https://codereview.chromium.org/14604003/ which has proven
difficult to land, so we're doing it in parts.

Review URL: https://chromiumcodereview.appspot.com/17191008

git-svn-id: svn://svn.chromium.org/blink/trunk@152857 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused includes from core/accessibility, core/css and core/dom

Continue removing unused includes as suggested by include-what-you-use.
I've manually looked through all the changes so all the removals should
be actually unused. As usual, if a .cpp only needs a fwd decl of a type
used in a method signature, I assume that the header would already have
included or declared the type and remove the include from the .cpp.

BUG=242216

Review URL: https://chromiumcodereview.appspot.com/17480002

git-svn-id: svn://svn.chromium.org/blink/trunk@152858 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Introduce toHTMLFormElement, and use it.

HTMLImageElement::insertedInto:
Use HTMLElement::findFormAncestor.

BUG=none
TEST=none; no behavior change.

Review URL: https://chromiumcodereview.appspot.com/17505005

git-svn-id: svn://svn.chromium.org/blink/trunk@152859 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert "RuleSet causes 600 kB of memory fragmentation"

This reverts commit c3a7797e3cde2c2dbe04b2c54d54740db169e966.

This caused 100 LayoutTests to crash on Mac 10.6 and 10.7 debug

BUG=252597
TBR=abarth

Review URL: https://codereview.chromium.org/17266003

git-svn-id: svn://svn.chromium.org/blink/trunk@152860 bbb929c8-8fbe-4397-9dbb-9b2b20218538