[rough WIP] Make View::GetEventHandlerForRect() non-virtual

[rough WIP] Make View::GetEventHandlerForRect() non-virtual

WIP

BUG=none

[tdanderson, 2014-07-10 23:50:24]

Sadrul, here is the rough WIP we discussed today along with a couple of
comments. Note that this also contains the code to replace View::HitTestRect()
overrides with ViewTargeterDelegate::DoesIntersectRect(), which I'm landing
first (https://codereview.chromium.org/380813003/).

To remind you of the main points from today's discussion:

* With this design, it doesn't look like ViewTargeter is able to use any of the
implementation in EventTargeter. This is unfortunate, since it was one of the
original goals.

* You wanted to take a closer look at the existing ~6 overrides of
View::GetEventHandlerForRect(). They are all in this CL.

* I believe the current code path for targeting scroll events is actually wrong
(see my inline comments).

* I am concerned that with this design, we don't get fuzzing for free everywhere
like I would have hoped. There may be a way to accomplish this, though, after
taking a closer look at the GetEventHandlerForRect() overrides and possibly
making ViewTargeter::TargetForRect() do more than just be a call-through.

https://codereview.chromium.org/381323002/diff/1/ui/views/view_targeter.cc
File ui/views/view_targeter.cc (right):

https://codereview.chromium.org/381323002/diff/1/ui/views/view_targeter.cc#ne...
ui/views/view_targeter.cc:49: return EventTargeter::FindTargetForEvent(root,
event);
This is the call I believe to be wrong as-is since it does not hook into the
overrides of GetEventHandlerForRect() in any way. It was landed two months ago
but I have not seen any regressions filed against it, though.

For scrolls (and eventually for gestures and mouse), I think this function
should actually just call into TargetForRect() instead of calling up to the
default implementation in EventTargeter.

https://codereview.chromium.org/381323002/diff/1/ui/views/view_targeter.cc#ne...
ui/views/view_targeter.cc:74: bool ViewTargeter::EventLocationInsideBounds(
Assuming that ViewTargeter::FindTargetForEvent() should be calling
TargetForRect() (see my comment on line 49), then this override of
EventLocationInsideBounds() can be deleted since the only time we actually call
it is from EventTargeter. Same for ViewTargeter::SubtreeCanAcceptEvent().

[tdanderson, 2014-07-16 15:37:39]

Sadrul, I have rebased against ToT so PS4 should now be much more readable.

I'd still like your thoughts on the points from my last message, but regardless
this is the right way to proceed for the time being so I am going to start
landing this in pieces. Improvements such as eliminating unnecessary overrides
of TargetForRect() can always come after the fact.