Add chrome://flags entry for MojoLoading

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 e2f1fe66946a8ecd23b0de605bf33a0b078c594a..0d4baaa80899a8a8b292911e24a2a630d0a5c906 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -99100,6 +99100,7 @@ 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="-1856902397" label="LoadingWithMojo:enabled"/>
   <int value="-1849706663" label="enable-password-force-saving:disabled"/>
   <int value="-1847835522" label="disable-touch-adjustment"/>
   <int value="-1847776781"
@@ -99172,6 +99173,7 @@ from previous Chrome versions.
   <int value="-1572010356" label="enable-privet-v3"/>
   <int value="-1571841513" label="enable-devtools-experiments"/>
   <int value="-1559789642" label="RunAllFlashInAllowMode:enabled"/>
+  <int value="-1557527869" label="LoadingWithMojo:disabled"/>
   <int value="-1553477903" label="ash-disable-text-filtering-in-overview-mode"/>
   <int value="-1546903171" label="enable-touch-drag-drop"/>
   <int value="-1544248549" label="ArcUseAuthEndpoint:enabled"/>