Remove CSS Custom Filters code and LayoutTests.

Originally authored by Adam Barth. Finished up by Max Vujovic.

Review URL: https://codereview.chromium.org/132873003

git-svn-id: svn://svn.chromium.org/blink/trunk@164847 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: Rename special case: EventTarget => EventHandler

A type that is a special case for is_keep_alive_for_gc was renamed.
Didn't catch this earlier b/c test was broken (missing readonly).
Fixed.

TBR=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/133173002

git-svn-id: svn://svn.chromium.org/blink/trunk@164848 bbb929c8-8fbe-4397-9dbb-9b2b20218538