Add first/last bounds for each WebInputEvent type class

|WebInputEvent::isFooEventType()| queries to determine an event's type class are
frequent, executed potentially 10-15 times or more over the lifetime of a single
event instance.  Speed this query by adding first/last enum bounds for each type
class, and changing the query from a chain of |if(type == Web*Event)| checks
into a simple bounds check.

In testing on several Android devices, the bounds check was 4x faster for a long
sequence of randomized type queries, and 2x faster than changing the chains into
switch statements. This also makes it easier to determine type counts for a
specific class.

BUG=341613

Review URL: https://codereview.chromium.org/170283012

git-svn-id: svn://svn.chromium.org/blink/trunk@167469 bbb929c8-8fbe-4397-9dbb-9b2b20218538