Add DomDistiller.PageDistilledType and update DD.PageDistillableType

This adds a new distallable type (mobile-friendly distillable) and adds
a histogram for tracking what types of pages are actually distilled.

BUG=444160

Review URL: https://codereview.chromium.org/900963003

Cr-Commit-Position: refs/heads/master@{#314956}

tools/metrics/actions/actions.xml

@@ -2557,7 +2557,7 @@ should be able to be added at any place in this file.
 <action name="DomDistiller_DistilledPageOpened">
   <owner>smaslo@chromium.org</owner>
   <owner>yfriedman@chromium.org</owner>
-  <description>User opens a distilled page.</description>
+  <description>User opens reader mode on a page.</description>
 </action>
 
 <action name="DomDistiller_DistilledPagePrefsOpened">

tools/metrics/histograms/histograms.xml

@@ -5461,11 +5461,19 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
-<histogram name="DomDistiller.PageDistillable" enum="BooleanDistillable">
-  <owner>yfriedman@chromium.org</owner>
+<histogram name="DomDistiller.PageDistillable" enum="DistillableType">
+  <owner>cjhopman@chromium.org</owner>
+  <summary>
+    Records the &quot;Distillable Type&quot; (not distillable, mobile-friendly
+    distillable, non-mobile-friendly distillable, etc) for each analyzed page.
+  </summary>
+</histogram>
+
+<histogram name="DomDistiller.PageDistilledType" enum="DistillableType">
+  <owner>cjhopman@chromium.org</owner>
   <summary>
-    Records the number of times a page was loaded for which using DomDistiller
-    is possible.
+    Records the &quot;Distillable Type&quot; (not distillable, mobile-friendly
+    distillable, non-mobile-friendly distillable, etc) for each distilled page.
   </summary>
 </histogram>
 
@@ -43568,11 +43576,6 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="1" label="Did fall back"/>
 </enum>
 
-<enum name="BooleanDistillable" type="int">
-  <int value="0" label="Not distillable"/>
-  <int value="1" label="Distillable"/>
-</enum>
-
 <enum name="BooleanDuplicate" type="int">
   <int value="0" label="Not Duplicate"/>
   <int value="1" label="Duplicate"/>
@@ -44911,6 +44914,12 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="3" label="Primary accounts present but different"/>
 </enum>
 
+<enum name="DistillableType" type="int">
+  <int value="0" label="Not distillable"/>
+  <int value="1" label="Non-mobile-friendly Distillable"/>
+  <int value="2" label="Mobile-friendly distillable"/>
+</enum>
+
 <enum name="DllHash" type="int">
 <!-- Generated by chrome_elf/dll_hash/dll_hash_main.cc -->