IDL compiler: sync setters to rename value => jsValue, v => cppValue

This updates the setters in:
IDL compiler: Basic setters
https://codereview.chromium.org/27638002/

...per the renamings in:
IDL compiler: rename value => jsValue, v => cppValue
https://codereview.chromium.org/26887006/

(Both CLs were in CQ at same time, hence need a sync.)

BUG=239771
NOTRY=true

Review URL: https://codereview.chromium.org/27923002

git-svn-id: svn://svn.chromium.org/blink/trunk@159930 bbb929c8-8fbe-4397-9dbb-9b2b20218538