[Feature Policy] Add command-line flag and about://flags interface for Feature Policy

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 7433988d4bfd71263a02cef5e001220482db84e0..564dc2d41c1ec2dd9d30b4944c2e470dd4869fea 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -15191,6 +15191,13 @@ read aloud to screenreader users to announce that a completion is available.">
       </message>
     </if>
 
+    <message name="IDS_FLAGS_FEATURE_POLICY_NAME" desc="Name for the flag to enable feature policy.">
+      Feature Policy
+    </message>
+    <message name="IDS_FLAGS_FEATURE_POLICY_DESCRIPTION" desc="Description for the flag to enable feature policy.">
+      Enables granting and removing access to features through the Feature-Policy HTTP header.
+    </message>
+
    <!-- Safe Browsing Subresource Filter UI strings. -->
     <if expr="use_titlecase">
       <message name="IDS_FILTERED_DECEPTIVE_CONTENT_PROMPT_OK" desc="In Title Case: button which dismisses the Content blocked prompt without performing any actions.">