GitLab

- Fix a bug that back gesture nudge dismiss metrics can be recorded even
  before back gesture nudge is shown.
- Fix a bug in BackGestureContextualNudgeControllerTest class, there are
  two BackGestureContextualNudgeControllerImpl instances.
- Fix several other tests in BackGestureContextualNudgeControllerTest.
- Add contextual_tooltip::DismissNudgeReason::kTimeout metrics back,
  which is logged after back nudge animation sequence is finished.
- Modify the timing to record contextual_tooltip::DismissNudgeReason::
  kPerformedGesture. Previously it's recorded after back gesture is
  finished, now it's recorded when back gesture starts.

Bug: 1101105
Change-Id: I6cd2b59bb0091892f9c24511c57d692e03272265
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2345705
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796914}