Drop NotEnumerable for the on* event handler IDL attributes

BUG=305112

Review URL: https://codereview.chromium.org/26117003

git-svn-id: svn://svn.chromium.org/blink/trunk@159721 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add some more ASSERTs to partitionAlloc.

Some memory corruption errors might be flagged sooner in debug builds now. In a
future CL, we might consider padding allocations with canaries in debug.

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/27217008

git-svn-id: svn://svn.chromium.org/blink/trunk@159722 bbb929c8-8fbe-4397-9dbb-9b2b20218538