Record data use of user traffic by different core page transition types

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 4e22c187711f934812506099cf16e385d94c65cb..24ed2bdb7e439e448d4ce8eed46a39c5d20924f2 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -9528,6 +9528,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="DataUse.PageTransition.UserTraffic"

[rkaplow, 2017/01/12 16:28:06]

I don't think this design is correct, since this way you won't know the
distribution of bytes, everything will get grouped together.

I think you want a separate histogram for eac page transition. You can use the
histogram_suffix notation in the xml file to help generate the correct config.
Each one will be a numeric histogram measuring it in bytes.

[Raj, 2017/02/14 22:52:51]

I thought about it. It will be 10+ histograms to log that. We are not planning
to look at distribution of bytes by page transition. We have
DataUse.TrafficSize.* histograms to get the general distribution of bytes.

WDYT.

+    enum="DataUsePageTransition" units="bytes">
+  <owner>rajendrant@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    Data use of user traffic by different core page transition types. Recorded
+    when the URL request finishes.
+  </summary>
+</histogram>
+
 <histogram name="DataUse.Sync.Download.Bytes" enum="SyncModelTypes">
   <owner>amohammadkhan@chromium.org</owner>
   <owner>bengr@chromium.org</owner>
@@ -81654,6 +81664,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="8" label="Data use tracking ended dialog opted out"/>
 </enum>
 
+<enum name="DataUsePageTransition" type="int">
+  <summary>PageTransitions in ui/base/page_transition_types.h.</summary>
+  <int value="0" label="LINK"/>
+  <int value="1" label="TYPED"/>
+  <int value="2" label="AUTO_BOOKMARK"/>
+  <int value="3" label="SUBFRAME"/>
+  <int value="4" label="GENERATED"/>
+  <int value="5" label="AUTO_TOPLEVEL"/>
+  <int value="6" label="FORM_SUBMIT"/>
+  <int value="7" label="RELOAD"/>
+  <int value="8" label="KEYWORD"/>
+  <int value="9" label="FORWARD_BACK"/>
+  <int value="10" label="HOME_PAGE"/>
+</enum>
+
 <enum name="DataUseServices" type="int">
   <int value="0" label="Not Tagged"/>
   <int value="1" label="Suggestions"/>