IDL compiler: Rename special case: EventTarget => EventHandler
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: bf5cd6ccde378db821296732a091cfbcf5285fbd@164848 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs