Add indication of camera use on SAML webcam logins

chrome/browser/resources/chromeos/login/screen_gaia_signin.html

Index: chrome/browser/resources/chromeos/login/screen_gaia_signin.html
diff --git a/chrome/browser/resources/chromeos/login/screen_gaia_signin.html b/chrome/browser/resources/chromeos/login/screen_gaia_signin.html
index fa503d2da82aaa3a976b28a9c5823f20615aad63..f1fba02171a3792175e34a07133a277407d873bf 100644
--- a/chrome/browser/resources/chromeos/login/screen_gaia_signin.html
+++ b/chrome/browser/resources/chromeos/login/screen_gaia_signin.html
@@ -18,6 +18,9 @@
                    link-label:learnMoreButton">
   </notification-card>
   <div id="saml-notice-container" hidden>
+    <span id="saml-notice-recording-indicator" hidden>
+      <img src="chrome://theme/IDR_RESET_WARNING">

[Kevin Cernekee, 2016/05/10 21:05:42]

This is the wrong icon.

I tried IDR_TAB_RECORDING_INDICATOR but it looks like all platforms except OSX
have switched this from a raster to a vector icon, so it is unavailable on
Chrome OS.

I think I want gfx::VectorIconId::TAB_MEDIA_RECORDING but I don't know how to
get to it from the UI HTML.  Any ideas on how to proceed?

[emaxx, 2016/05/13 17:44:03]

I haven't found any way how the vector icon can be requested from an HTML page
(though probably worth asking estade@ - the /ui/gfx/vector_icons/ owner).

Otherwise the necessary IDR_TAB_RECORDING_INDICATOR raster icon could be
requested for Chrome OS too (looks like this stuff is configured in the
/chrome/app/theme/theme_resources.grd file).

[Kevin Cernekee, 2016/05/13 18:39:04]

Done.

+    </span>
     <span id="saml-notice-message"></span>
   </div>
   <navigation-bar id="gaia-navigation"></navigation-bar>