This patch fixes up one last case of redundant ExceptionEvents being
triggered in the debugger for Promises--it makes the default reject
handler for Promises (e.g., if the second argument for
Promise.prototype.then is missing) appear to the debugger as a
rethrow.

R=adamk@chromium.org,jgruber@chromium.org
BUG=v8:5167

Review-Url: https://codereview.chromium.org/2278643002
Cr-Commit-Position: refs/heads/master@{#38876}