Add flag for AIA fetching and enable on waterfall

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 db0258319ce14ea934ea95de8bf9efb534e836ed..6b85901386f5fff1b04f16610f037fa5c388192f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -96510,6 +96510,7 @@ value.
   <int value="-213518852" label="protect-sync-credential:enabled"/>
   <int value="-206393363" label="enable-scroll-prediction"/>
   <int value="-204355195" label="secondary-ui-md"/>
+  <int value="-202007318" label="AndroidAIAFetching:enabled"/>
   <int value="-195029497" label="MediaRemoting:disabled"/>
   <int value="-192919826" label="ViewsSimplifiedFullscreenUI:enabled"/>
   <int value="-192389983" label="NoStatePrefetch:enabled"/>
@@ -96832,6 +96833,7 @@ value.
   <int value="1257980502" label="disable-accelerated-video-decode"/>
   <int value="1268470658" label="disable-android-password-link"/>
   <int value="1269940659" label="EnumerateAudioDevices:enabled"/>
+  <int value="1269952439" label="AndroidAIAFetching:disabled"/>
   <int value="1272699563" label="enable-hosted-mode"/>
   <int value="1276209777" label="ntp-switch-to-existing-tab"/>
   <int value="1279584261" label="enable-carrier-switching"/>