Make chrome://flags control whether the WebAPK feature is on

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 686021c772acdef887fefc302993b362f62fff11..0595e7fd4389a1a746350f028ec36089cdc4a0e8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -93203,6 +93203,7 @@ value.
   <int value="-907234795" label="NewAudioRenderingMixingStrategy:disabled"/>
   <int value="-899334103" label="disable-fast-text-autosizing"/>
   <int value="-898594349" label="ash-enable-stable-overview-order"/>
+  <int value="-898499262" label="ImprovedA2HS:enabled"/>
   <int value="-898005938" label="disable-pinch-virtual-viewport"/>
   <int value="-894214299" label="fill-on-account-select:enabled"/>
   <int value="-891856063" label="MidiManagerAndroid:enabled"/>
@@ -93296,6 +93297,7 @@ value.
   <int value="-430360431" label="disable-password-generation"/>
   <int value="-428599163" label="NTPDownloadSuggestions:enabled"/>
   <int value="-418868128" label="enable-experimental-web-platform-features"/>
+  <int value="-410852857" label="ImprovedA2HS:disabled"/>
   <int value="-396994784" label="enable-vr-shell"/>
   <int value="-395606844" label="enable-site-settings"/>
   <int value="-387606010" label="ArcBootCompletedBroadcast:enabled"/>