Update offline pages UMAs

chrome/browser/android/offline_pages/offline_page_tab_helper.cc

Index: chrome/browser/android/offline_pages/offline_page_tab_helper.cc
diff --git a/chrome/browser/android/offline_pages/offline_page_tab_helper.cc b/chrome/browser/android/offline_pages/offline_page_tab_helper.cc
index f818cf64c8cd76c578e390e6ca70bdb5b980c2f4..f5e6c796f4d9c7d3eb8467f63afd1d6e3febda74 100644
--- a/chrome/browser/android/offline_pages/offline_page_tab_helper.cc
+++ b/chrome/browser/android/offline_pages/offline_page_tab_helper.cc
@@ -53,6 +53,9 @@ void OfflinePageTabHelper::DidStartNavigation(
     // immediate redirection to offline copy.
     redirect_url = offline_pages::OfflinePageUtils::GetOfflineURLForOnlineURL(
       web_contents()->GetBrowserContext(), navigation_handle->GetURL());
+
+    UMA_HISTOGRAM_BOOLEAN("OfflinePages.ShowOfflinePageWhenOffline",

[fgorski, 2016/05/16 16:20:04]

can we report with suffix here? It would be interesting to learn which URL gets
selected.

This can be done inside of the OfflinePageUtils::GetOfflineURLForOnlineURL, or
as part of the selection process in:
OfflinePageModel::MaybeGetBestPageForOnlineURL

[jianli, 2016/05/16 22:35:25]

I thought about this but we can't do it because no suffix can be used if no
offline URL is found.

+                          redirect_url.is_valid());
   } else {
     // When the network is connected, loading offline copy will result in
     // immediate redirection to online page.