The handling of wasm breakpoints was prone to forget previously set
breakpoints when inserting new ones. In particular, adding breakpoints
in reverse order or adding more than 4 breakpoints would fail.

Change-Id: I94f314e86bdf9b53a4170ce1b6b47339b7cb7848
Reviewed-on: https://chromium-review.googlesource.com/1019302Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52691}