The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/451e96e37d9398a600f232cd6830fa3013f2d7a5

commit 451e96e37d9398a600f232cd6830fa3013f2d7a5
Author: Fadi Meawad <fmeawad@chromium.org>
Date: Wed Oct 11 19:27:56 2017

[Memory UKM] Add IsVisible, TimeSinceLastVisibilityChange and TimeSinceLastNavigation to the Memory UKM Record

This CL does the follow:
* It removes the local PageData from the MetricsCollector
  (including last_invisible_time and navigation_finished_time)
* Adds the new fields to PageCoordinationUnitImpl
* Merges the new fields with UkmSourceId into a new PageInfo
  mojo struct in CoordinationUnitIntrospectorImpl
* Add the new values to ProcessMemoryMetricsEmitter to be included
  as part of the UKM record.
* cleanup: Remove kURL from singals.mojom since it is no longer used.

Bug:  chromium:764098 , chromium:757873 
Change-Id: I53cc6e85fc991cf27c8dc45fb6b38a67c0901a19
Reviewed-on: https://chromium-review.googlesource.com/666295
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Reviewed-by: lpy <lpy@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Fadi Meawad <fmeawad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508065}
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/chrome/browser/metrics/process_memory_metrics_emitter.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/chrome/browser/metrics/process_memory_metrics_emitter_browsertest.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/chrome/browser/metrics/process_memory_metrics_emitter_unittest.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/coordination_unit/coordination_unit_introspector_impl.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/coordination_unit/page_coordination_unit_impl.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/coordination_unit/page_coordination_unit_impl.h
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/coordination_unit/page_coordination_unit_impl_unittest.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/observers/metrics_collector.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/observers/metrics_collector.h
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/observers/metrics_collector_unittest.cc
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/public/interfaces/coordination_unit_introspector.mojom
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/services/resource_coordinator/public/interfaces/signals.mojom
[modify] https://crrev.com/451e96e37d9398a600f232cd6830fa3013f2d7a5/tools/metrics/ukm/ukm.xml