The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2b1e1bf1a312185ac0162c31805b49333fc1cb3b

commit 2b1e1bf1a312185ac0162c31805b49333fc1cb3b
Author: shaseley <shaseley@google.com>
Date: Fri Jun 16 18:38:57 2017

[Tab Metrics] Adding the tab loading state to the WebContentsData.

Adding the tab loading state as a preliminary step for adding the number of
switches to not loading, loading, and loaded tabs during session restore and
background tab loading.

Initially, the tab/WebContentsData starts as not loaded. We consider the tab to
be loading when the main frame begins a navigation. This happens with the
initial page navigation, if a page refreshes itself, or if navigating to a new
page and the WebContents is being reused. This does not include cases where
individual iframes update content after the page is loaded. The tab is
considered to be loaded when receiving the WebContentsObserver::DidStopLoading
signal, which corresponds to when the spinner stops.

BUG= 732837 

Review-Url: https://codereview.chromium.org/2936003002
Cr-Commit-Position: refs/heads/master@{#480108}

[modify] https://crrev.com/2b1e1bf1a312185ac0162c31805b49333fc1cb3b/chrome/browser/resource_coordinator/tab_manager_web_contents_data.cc
[modify] https://crrev.com/2b1e1bf1a312185ac0162c31805b49333fc1cb3b/chrome/browser/resource_coordinator/tab_manager_web_contents_data.h
[modify] https://crrev.com/2b1e1bf1a312185ac0162c31805b49333fc1cb3b/chrome/browser/resource_coordinator/tab_manager_web_contents_data_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/97e4ec20d584f59fe5a701cde8b29257b0a0b31d

commit 97e4ec20d584f59fe5a701cde8b29257b0a0b31d
Author: shaseley <shaseley@google.com>
Date: Thu Jun 29 22:45:49 2017

[Tab Metrics] Added TabManager.SessionRestore.SwitchToTab UMA.

This is the first of two metrics recorded in the TabManager when switching to a
different tab. If there is currently a session restore in progress and the user
switches tabs, we emit an UMA histogram recording the tab loading state. As a
follow-up, we'll add a separate UMA if the TabManager is in a background tab
loading state, once the tab manager has that functionality.

BUG= 732837 

Review-Url: https://codereview.chromium.org/2962773002
Cr-Commit-Position: refs/heads/master@{#483525}

[modify] https://crrev.com/97e4ec20d584f59fe5a701cde8b29257b0a0b31d/chrome/browser/resource_coordinator/tab_manager.cc
[modify] https://crrev.com/97e4ec20d584f59fe5a701cde8b29257b0a0b31d/chrome/browser/resource_coordinator/tab_manager.h
[modify] https://crrev.com/97e4ec20d584f59fe5a701cde8b29257b0a0b31d/chrome/browser/resource_coordinator/tab_manager_unittest.cc
[modify] https://crrev.com/97e4ec20d584f59fe5a701cde8b29257b0a0b31d/chrome/browser/resource_coordinator/tab_manager_web_contents_data.h
[modify] https://crrev.com/97e4ec20d584f59fe5a701cde8b29257b0a0b31d/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/97e4ec20d584f59fe5a701cde8b29257b0a0b31d/tools/metrics/histograms/histograms.xml