Limit number of fragments scored if possible

Since the best fragments are typically at the beginning of the article any
way we can relatively safely stop searching for matches after 50 fragments.
This should help with really crazy documents, say 10MB of "d d".  Without
this we'll scan out all the "d"s on a search for "d". With it, only the
first 50.

Only works for experimental highlighter because, well, only the experimental
highlighter has this feature.

Change-Id: I09b9718ee84fb4cf30178b9b2949f55513b3f448
Remove debugging log

Change-Id: I2c3957ebfb08119612f5d62d3fa07ae6350f5190
Merge "Remove debugging log"