Remove some abstractions in fxjs_v8.h.

Remove some abstractions in fxjs_v8.h.

It's too hard to keep mapping between v8 and fx abstractions; the lack
of transparency prevents those skilled in v8 only from working on this
code.

Apparently, the original intention was to confine v8 types to
fpdfsdk/{include,src}/jsapi, but fpdfsdk/{include,src}/javascript
is already well-polluted with v8 types.

Also remove no-op JS_SetThisObj().

Also remove unused ParserParams() [noticed because it was incorrectly
passing handles as pointers].

Also remove cast operator from CJS_Runtime and call GetIsolate()
explicitly.

R=thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/6df59849472958e7de96da6d9fc7b223b7c1f1c3

[Tom Sepez, 2015-09-10 18:03:39]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-09-10 18:03:40]

Lei, for review.  I was trying to write fxjs_v8 tests, but couldn't keep all the
objects straight in my mind, so lets do this first.

[Lei Zhang, 2015-09-10 18:47:14]

lgtm

[Tom Sepez, 2015-09-10 18:56:43]

Committed patchset #8 (id:140001) manually as
6df59849472958e7de96da6d9fc7b223b7c1f1c3 (presubmit successful).