Create new EventHandler and base class for EventListener/EventHandler

This CL implements these classes in Blink:
JSBasedEventListener                       (The base class for
 |                                          EventLisntener/EventHandler)
 +- JSEventListener                        (Implements EventListener)
 +- JSEventHandler                         (Implements EventHandler and
     |                                      other special types)
     +- JSEventHandlerForContentAttribute  (Supports lazy compilation
                                            for content attribute)
EventHandlers start to support incumbent realm using
blink::V8EventHandlerNonNull that inherits blink::CallbackFunctionBase.
(EventListener already supports incumbent realm.)

These four classes are no longer referenced from anywhere:
  blink::V8AbstractEventListener
  blink::V8EventListenerOrEventHandler
  blink::V8ErrorHandler
  blink::V8LazyEventListener
Although these are no longer necessary, this CL does not remove them
so that we can easily switch which classes to use in case new classes
contains some problems.

regarding crbug.com/759461 :
OnErrorEventHandler for content attribute, which has different number
of arguments, gets supported by blink::JSEventHandler and
blink::JSEventHandlerForContentAttribute.

regarding crbug.com/664676 :
|js_event| in the relevant realm of |event|'s target is created in
blink::JSBasedEventListener::handleEvent().

Bug: 872138, 849236, 759461, 664676, 606900
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I356734fc16611277ad9f3f279a676e7dc8083408
Reviewed-on: https://chromium-review.googlesource.com/c/1215512
Commit-Queue: Yuki Yamada <yukiy@google.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hayato Ito <hayato@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597054}
50 files changed