Add baked-in favicons for default popular sites on NTP

components/ntp_tiles/popular_sites.h

Index: components/ntp_tiles/popular_sites.h
diff --git a/components/ntp_tiles/popular_sites.h b/components/ntp_tiles/popular_sites.h
index dde8459ba5b2c74db311b268852b52fb35d8d775..77d5f6b5ffcde15cba448c51e2c2fa75fb503f57 100644
--- a/components/ntp_tiles/popular_sites.h
+++ b/components/ntp_tiles/popular_sites.h
@@ -37,6 +37,7 @@ class PopularSites {
     GURL favicon_url;
     GURL large_icon_url;
     GURL thumbnail_url;
+    int default_resource_id;  // <0 if there is none. Used for popular defaults.

[mastiz, 2017/03/01 08:48:12]

Rename such that the term 'icon' is part of the name? IIUC, this is only about
the icon.

[mastiz, 2017/03/01 08:48:12]

Did you choose -1 because 0 is a valid resource id? If not, 0 would be more
appropriate, since it's the default value of ints.

[fhorschig, 2017/03/01 20:57:35]

I was asked to change from -1 to 0. Partly because it shouldn't be a
valid default.

[fhorschig, 2017/03/01 20:57:35]

Done.

[mastiz, 2017/03/02 11:05:39]

Did you mean from 0 to -1? Is 0 a valid resource ID?

[fhorschig, 2017/03/02 11:56:24]

Yes, this is what I meant. 0 is (technically) valid although all resources
are assigned ranges [a,b] with 0 < a < b.

   };
 
   using SitesVector = std::vector<Site>;