GMC: Update enums.xml for new media session actions

Bug: 1048902
Change-Id: I5c7d4d94fed28d7943fd7bdf96be31856580e44c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2038073Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738621}

tools/metrics/histograms/enums.xml

@@ -42355,6 +42355,9 @@ Called by update_use_counter_css.py.-->
   <int value="6" label="Skip Ad"/>
   <int value="7" label="Stop"/>
   <int value="8" label="Seek To"/>
+  <int value="9" label="Scrub To"/>
+  <int value="10" label="Enter picture in picture"/>
+  <int value="11" label="Exit picture in picture"/>
 </enum>
 
 <enum name="MediaSessionActionSource">