As discussed in https://codereview.chromium.org/2936723002/, we want to count the number of calls to UpdateForSameDocumentNavigation according to SinglePageAppNavigationType instead.

Depending on same_document_navigation_source and FrameLoadType, single page app navigation types can be split into SameDocumentBackwardOrForward, HistoryApi and HistoryPushStateOrReplaceState. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/772ace0703fb420097d1c14b53a5f186d2027771

commit 772ace0703fb420097d1c14b53a5f186d2027771
Author: maxlg <maxlg@chromium.org>
Date: Tue Jul 04 20:44:38 2017

Report frequency of single page app navigations to UMA

We currently output a trace event for each single page app navigation. This
change is to record that for UMA as well.

BUG= 720550 

Review-Url: https://codereview.chromium.org/2936723002
Cr-Commit-Position: refs/heads/master@{#484153}

[modify] https://crrev.com/772ace0703fb420097d1c14b53a5f186d2027771/third_party/WebKit/Source/core/loader/FrameLoader.cpp
[modify] https://crrev.com/772ace0703fb420097d1c14b53a5f186d2027771/third_party/WebKit/Source/core/loader/FrameLoaderTypes.h
[modify] https://crrev.com/772ace0703fb420097d1c14b53a5f186d2027771/third_party/WebKit/Source/web/tests/WebFrameTest.cpp
[modify] https://crrev.com/772ace0703fb420097d1c14b53a5f186d2027771/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/772ace0703fb420097d1c14b53a5f186d2027771/tools/metrics/histograms/histograms.xml