Add UMA logging of extension creation flags.

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 e172e6bc64845865971ed12a2632bbd4324bf863..c6c2b066a17bfb48b04121e9ec01b792b7ae4568 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6090,6 +6090,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.LoadCreationFlags" enum="ExtensionCreationFlags">
+  <owner>calamity@chromium.org</owner>
+  <summary>
+    The creation flags of all extensions loaded at startup time grouped by
+    Extension::InitFromValueFlags.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.LoadExtension">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>The number of extensions loaded at browser startup.</summary>
@@ -32603,6 +32611,20 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="2" label="Event Page"/>
 </enum>
 
+<enum name="ExtensionCreationFlags" type="int">
+  <int value="1" label="REQUIRE_KEY"/>
+  <int value="2" label="REQUIRE_MODERN_MANIFEST_VERSION"/>
+  <int value="3" label="ALLOW_FILE_ACCESS"/>
+  <int value="4" label="FROM_WEBSTORE"/>
+  <int value="5" label="FROM_BOOKMARK"/>
+  <int value="6" label="FOLLOW_SYMLINKS_ANYWHERE"/>
+  <int value="7" label="ERROR_ON_PRIVATE_KEY"/>
+  <int value="8" label="WAS_INSTALLED_BY_DEFAULT"/>
+  <int value="9" label="REQUIRE_PERMISSIONS_CONSENT"/>
+  <int value="10" label="IS_EPHEMERAL"/>
+  <int value="11" label="WAS_INSTALLED_BY_OEM"/>
+</enum>
+
 <enum name="ExtensionDisabledUIUserResponse" type="int">
   <int value="0" label="IGNORED"/>
   <int value="1" label="REENABLE"/>