Drop computed handler count and index from AST.

Drop computed handler count and index from AST.

These values were computed by the parser and hence out of sync with any
visitor over the AST. Our AST visitor aborts visitation of statement
lists as soon as a jump statement has been reached. Now handler tables
are guaranteed to be dense and fully populated.

R=ishell@chromium.org
TEST=mjsunit/regress/regress-crbug-493290
BUG=chromium:493290
LOG=N

Review URL: https://codereview.chromium.org/1157213004

Cr-Commit-Position: refs/heads/master@{#28846}