[Doodle] Add an about:flags entry for the new Doodle API

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 d775fe370baa72d8e51fa520cd9dd419e70a9336..a08e9f0f9fa3ad762f80e429c7267af3d98318ea 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -99749,6 +99749,7 @@ from previous Chrome versions.
   <int value="-1052415111" label="malware-interstitial-v2"/>
   <int value="-1052219252" label="disable-captive-portal-bypass-proxy"/>
   <int value="-1045900007" label="NoCreditCardAbort:disabled"/>
+  <int value="-1045882995" label="UseNewDoodleApi:enabled"/>
   <int value="-1041650038" label="enable-forced-migration-to-tabbed-mode"/>
   <int value="-1039889738" label="NativeNotifications:enabled"/>
   <int value="-1039555838" label="GamepadExtensions:enabled"/>
@@ -99819,6 +99820,7 @@ from previous Chrome versions.
   <int value="-795600188" label="disable-async-dns"/>
   <int value="-790036192" label="overscroll-start-threshold"/>
   <int value="-780798969" label="disable-single-click-autofill"/>
+  <int value="-775321548" label="UseNewDoodleApi:disabled"/>
   <int value="-770319039" label="enable-touch-editing"/>
   <int value="-763759697" label="enable-audio-support-for-desktop-share"/>
   <int value="-759830869" label="enable-tab-discarding"/>