🏠 Add expand button and flag to enable it

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 bfb4c9f8318b409301e8d416f3cbe24f677ed5d7..08fa618f9d4b230191912a744f1eb565beb36b13 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -86276,6 +86276,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="0" label="Swipe"/>
   <int value="1" label="Omnibox Focus"/>
   <int value="2" label="New Tab Creation"/>
+  <int value="3" label="Expand Button Pressed"/>
 </enum>
 
 <enum name="ChromeNotifierServiceActionType" type="int">
@@ -103293,6 +103294,7 @@ from previous Chrome versions.
   <int value="-1867382602" label="WebRTC-H264WithOpenH264FFmpeg:enabled"/>
   <int value="-1867342522" label="MaterialDesignHistory:enabled"/>
   <int value="-1861814223" label="MidiManagerDynamicInstantiation:enabled"/>
+  <int value="-1860481724" label="ChromeHomeExpandButton:enabled"/>
   <int value="-1856902397" label="LoadingWithMojo:enabled"/>
   <int value="-1849706663" label="enable-password-force-saving:disabled"/>
   <int value="-1847835522" label="disable-touch-adjustment"/>
@@ -104183,6 +104185,7 @@ from previous Chrome versions.
   <int value="1658644418" label="disable-app-list-voice-search"/>
   <int value="1661925474" label="silent-debugger-extension-api"/>
   <int value="1668611601" label="enable-encrypted-media"/>
+  <int value="1673427566" label="ChromeHomeExpandButton:disabled"/>
   <int value="1689123607" label="enable-app-link"/>
   <int value="1689183477" label="enable-merge-key-char-events"/>
   <int value="1691568199" label="AndroidSpellCheckerNonLowEnd:disabled"/>