Update chrome:// host whitelisting with the network service enabled.

For component platform apps, favicon, extension-icon, resources and
theme hosts are whitelisted for the chrome scheme. However, in the
network-service-enabled codepath, at most two of those hosts are passed
in |allowed_webui_hosts|, leaving out the other two for component
platform apps. Change the structure to more-closely match the
non-network-service codepath, whitelisting the four hosts when
appropriate.

Bug: 837328
Change-Id: Ib10e8fa2dcca0cf77be565bab3ebf9dd87daf188
Reviewed-on: https://chromium-review.googlesource.com/1201510Reviewed-by: Anand Mistry <amistry@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588326}

chrome/browser/chrome_content_browser_client.cc

@@ -4453,26 +4453,26 @@ void ChromeContentBrowserClient::
   if (!extension)
     return;
 
+  std::vector<std::string> allowed_webui_hosts;
   // Support for chrome:// scheme if appropriate.
   if ((extension->is_extension() || extension->is_platform_app()) &&
       Manifest::IsComponentLocation(extension->location())) {
     // Components of chrome that are implemented as extensions or platform apps
     // are allowed to use chrome://resources/ and chrome://theme/ URLs.
-    base::flat_set<std::string> allowed_webui_hosts = {
-        content::kChromeUIResourcesHost, chrome::kChromeUIThemeHost};
-    factories->emplace(
-        content::kChromeUIScheme,
-        content::CreateWebUIURLLoader(frame_host, content::kChromeUIScheme,
-                                      std::move(allowed_webui_hosts)));
-  } else if (extension->is_extension() || extension->is_legacy_packaged_app() ||
-             (extension->is_platform_app() &&
-              Manifest::IsComponentLocation(extension->location()))) {
+    allowed_webui_hosts.emplace_back(content::kChromeUIResourcesHost);
+    allowed_webui_hosts.emplace_back(chrome::kChromeUIThemeHost);
+  }
+  if (extension->is_extension() || extension->is_legacy_packaged_app() ||
+      (extension->is_platform_app() &&
+       Manifest::IsComponentLocation(extension->location()))) {
     // Extensions, legacy packaged apps, and component platform apps are allowed
     // to use chrome://favicon/ and chrome://extension-icon/ URLs. Hosted apps
     // are not allowed because they are served via web servers (and are
     // generally never given access to Chrome APIs).
-    base::flat_set<std::string> allowed_webui_hosts = {
-        chrome::kChromeUIExtensionIconHost, chrome::kChromeUIFaviconHost};
+    allowed_webui_hosts.emplace_back(chrome::kChromeUIExtensionIconHost);
+    allowed_webui_hosts.emplace_back(chrome::kChromeUIFaviconHost);
+  }
+  if (!allowed_webui_hosts.empty()) {
     factories->emplace(
         content::kChromeUIScheme,
         content::CreateWebUIURLLoader(frame_host, content::kChromeUIScheme,