[Extensions Click-to-Script] Add help article in chrome://extensions

Add a link to the help article for runtime host permissions in
the chrome://extensions page.

Note: the article that lives at this page is currently a placeholder,
and will be updated on the server.

Bug: 877664

Change-Id: Idc46b063d502b99458457679f279fa8d10e8e131
Reviewed-on: https://chromium-review.googlesource.com/1220473
Reviewed-by: Demetrios Papadopoulos <[email protected]>
Reviewed-by: Karan Bhatia <[email protected]>
Commit-Queue: Devlin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#591530}
diff --git a/chrome/browser/extensions/BUILD.gn b/chrome/browser/extensions/BUILD.gn
index 6fffa61..3246039 100644
--- a/chrome/browser/extensions/BUILD.gn
+++ b/chrome/browser/extensions/BUILD.gn
@@ -472,6 +472,8 @@
     "chrome_content_verifier_delegate.h",
     "chrome_extension_api_frame_id_map_helper.cc",
     "chrome_extension_api_frame_id_map_helper.h",
+    "chrome_extension_browser_constants.cc",
+    "chrome_extension_browser_constants.h",
     "chrome_extension_chooser_dialog.h",
     "chrome_extension_function.cc",
     "chrome_extension_function.h",