Remove safe_browsing=2 functionality, replace with =3 mode.

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 dc2b68ec8a7e3c69dacc8738228290486d360898..a80d80cfac9d7f66a24f746f64fd99a458f10d16 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -38126,6 +38126,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="SafeBrowsing.EnabledSettingChanged" enum="BooleanEnabled">
   <owner>feng@chromium.org</owner>
+  <obsolete>
+    Not in the code anymore (10/2015).
+  </obsolete>
   <summary>
     Records the user action that enables/disables safe browsing feature in the
     Settings page on Android.
@@ -39177,7 +39180,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="SB2.UpdateSizeBackground" units="bytes">
-  <owner>feng@chromium.org</owner>
+  <owner>nparker@chromium.org</owner>
+  <obsolete>
+    Was used for an experiment in late 2014.
+  </obsolete>
   <summary>
     The size of all the chunk URLs in an update response when Chrome is in the
     background.
@@ -39185,7 +39191,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="SB2.UpdateSizeForeground" units="bytes">
-  <owner>feng@chromium.org</owner>
+  <owner>nparker@chromium.org</owner>
+  <obsolete>
+    Was used for an experiment in late 2014.
+  </obsolete>
   <summary>
     The size of all the chunk URLs in an update response when Chrome is in the
     foreground.