Add a policy to re-enable deprecated web platform features.

chrome/browser/renderer_preferences_util.cc

Index: chrome/browser/renderer_preferences_util.cc
diff --git a/chrome/browser/renderer_preferences_util.cc b/chrome/browser/renderer_preferences_util.cc
index 9461c3a889b5d752bcb4c745496f44488fcddc5a..bf9c0b26b7cbde3efb7d7ae365a27dbd8928aa38 100644
--- a/chrome/browser/renderer_preferences_util.cc
+++ b/chrome/browser/renderer_preferences_util.cc
@@ -84,6 +84,22 @@ void UpdateFromSystemSettings(
       pref_service->GetBoolean(prefs::kEnableDoNotTrack);
   prefs->default_zoom_level = pref_service->GetDouble(prefs::kDefaultZoomLevel);
 
+  prefs->deprecated_features_to_enable.clear();
+  prefs->deprecated_features_to_enable.resize(
+      content::RENDERER_PREFERENCES_DEPRECATED_FEATURE_COUNT, false);
+  const base::ListValue* deprecated_features_list =
+      pref_service->GetList(prefs::kEnableDeprecatedWebPlatformFeatures);
+  for (base::ListValue::const_iterator feature(
+           deprecated_features_list->begin());
+       feature != deprecated_features_list->end();
+       ++feature) {
+    int value = -1;
+    if ((*feature)->GetAsInteger(&value) && value >= 0 &&
+        value < content::RENDERER_PREFERENCES_DEPRECATED_FEATURE_COUNT) {

[Andrew T Wilson (Slow), 2014/05/08 11:32:45]

Hmmm. Should the bounds check be a DCHECK instead?

[Mattias Nissler (ping if slow), 2014/05/09 16:38:27]

Well, pref values are not guaranteed to be totally under Chrome's control in
general, so I prefer this version to make absolutely sure we don't write out of
bounds.

+      prefs->deprecated_features_to_enable[value] = true;
+    }
+  }
+
 #if defined(TOOLKIT_GTK)
   GtkThemeService* theme_service = GtkThemeService::GetFrom(profile);
   prefs->focus_ring_color = theme_service->get_focus_ring_color();