Remove DocumentMarker::IsActiveMatch() and SetIsActiveMatch() methods

In https://codereview.chromium.org/2904093002 I'm moving the storage for the
MatchStatus flag from a subclass of DocumentMarkerDetails into TextMatchMarker.
This CL follows up by removing the getter/setter methods for this flag from
DocumentMarker, forcing callers to cast to TextMatchMarker. This helps clarify
where callers are making assumptions about the types of certain DocumentMarkers.

BUG=707867
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2909553002
Cr-Commit-Position: refs/heads/master@{#476142}
14 files changed