All uses of ParseMemberExpression go through
ParseMemberWithNewPrefixesExpression, and ParseMemberExpression always starts
with ParsePrimaryExprssion, so we can simply move Token::NEW handling into
ParsePrimaryExpression. That avoids an unnecessary branch on the hot path.

Change-Id: I2bcce8e106c547c6d308ee6b0fce8747c7214886
Reviewed-on: https://chromium-review.googlesource.com/c/1485838Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59827}