Fix WebAPK UKM XML definitions (add <statistics>).

My original CL
https://chromium-review.googlesource.com/c/chromium/src/+/1708416
left out some <statistics> tags inside the <history> tags. I think
I got them all.

Bug: 982362
Change-Id: Ia5c178c5ab2ab07f4ef6ab4012bf72c90616ecf1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1714369Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Glenn Hartmann <hartmanng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680171}

tools/metrics/ukm/ukm.xml

@@ -6232,6 +6232,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -7819,6 +7822,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -7847,6 +7853,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -7869,6 +7878,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -7925,6 +7937,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -7988,6 +8003,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -8010,6 +8028,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>
@@ -8038,6 +8059,9 @@ be describing additional metrics about the same event.
         <index fields="profile.country"/>
         <index fields="profile.form_factor"/>
         <index fields="profile.system_ram"/>
+        <statistics>
+          <quantiles type="std-percentiles"/>
+        </statistics>
       </history>
     </aggregation>
   </metric>