We're getting ready to remove page_load_histograms.h/.cc.
As part of that work, we can remove code that will be dead as a result of these files going away.
For example, the following properties in DocumentState are only needed by page_load_histograms:
web_timing_histograms_recorded
load_histograms_recorded
commit_load_time
first_paint_time
first_paint_after_load_time
finish_load_time
load_type
extensions::Dispatcher::WasWebRequestUsedBySomeExtensions can be removed
RenderThread::UpdateHistograms can be removed
Comment 1 by bmcquade@chromium.org
, Oct 21 2016