Amend merged revision history after rewrite.

We had to rewrite the history for
external/chromium_org/third_party/WebKit after the Blink merge, so these
old merged revision entries refer to commits that no longer exist.
Delete them to avoid confusing the merge script.

Change-Id: I40adda6b46d855615fb216cae8690fca3b4d84e4
1 file changed