cc: Don't attempt main thread synchronization if it is slow.

This patch:
1) Adds a critical_begin_main_frame_to_activate_is_fast flag.
2) Separates impl_latency_takes_priority_ into tree_priority_
   and a scroll_handler_state_.
3) Replaces impl_latency_takes_priority with
   ImplLatencyTakesPriority(), which is now a function of
   the above and is now true when the main thread is too slow.

There is also a small change to the latency recovery logic that
estimates the main thread response time depending on whether
the the BeginMainFrame is critical or not.

BUG=469953
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1425973003

Cr-Commit-Position: refs/heads/master@{#360500}

0 files changed, 0 insertions, 0 deletions