Chrome Version: 57.0.2986.0
OS: All

What steps will reproduce the problem?
(1) Load any full-page PDF.
(2) Use find-in-page function to search for something on the page multiple times.
(3) Observe the resulting FindReply IPCs directly.

Essentially, for all regular pages, find next requests are replied to with two FindReply IPCs: the first to update the active match ordinal for the new match, and the second to report/confirm the number of matches and specify that it is the final update (to indicate that the total number of matches has not changed since the last search, and that no other replies are coming).

However, in the case of a PDF page, searching is handled by a PDF-specific find plugin instead of the regular infrastructure, and it behaves a bit differently. For initial find requests, the find replies look to be the same as for a regular page, but for find next requests, the plugin returns only a single reply with the new active match ordinal, and never specifies which reply is final. I discovered that this confuses tests, and probably other things as well that I haven't noticed.