Revert "Implement script-side of callback reactions for Custom Elements V1"

This reverts commit 4f581ae17af347201ede92b01dc47068ee0cf2d5.

This commit landed twice, and the second landing caused a function to be defined
twice in V8Binding.h.

BUG=594918
TBR=kojii@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2066793003
Cr-Commit-Position: refs/heads/master@{#399866}
1 file changed