Add boolean to UserIntiatedInfo noting if an input event led to navigation.

Also refactor UkmPageLoadMetricsObserver to use this new boolean to
report the user initiated metric in RecordPageLoadExtraInfoMetrics, so
that it works correctly in the case when the page load failed.

Bug: 925104
Change-Id: Ie08e7d3912cb1da484190d838005e95e57a209ff
Reviewed-on: https://chromium-review.googlesource.com/c/1450460
Commit-Queue: Annie Sullivan <sullivan@chromium.org>
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630870}
void MetricsWebContentsObserver::RemoveTestingObserver(
    TestingObserver* observer) {
  testing_observers_.RemoveObserver(observer);
}

void MetricsWebContentsObserver::RemoveTestingObserver(
    TestingObserver* observer) {
  testing_observers_.RemoveObserver(observer);
}
