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

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 10c86804ebb0a9b82d170523f813663b1c6a7c08..a0a7bc13520e199b2437f70d5942f9d462b7e273 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -243,8 +243,8 @@
 #include "chrome/browser/local_discovery/storage/privet_filesystem_backend.h"
 #endif
 
-using blink::WebWindowFeatures;
 using base::FileDescriptor;
+using blink::WebWindowFeatures;
 using content::AccessTokenStore;
 using content::BrowserChildProcessHostIterator;
 using content::BrowserThread;
@@ -657,6 +657,9 @@ void ChromeContentBrowserClient::RegisterProfilePrefs(
       prefs::kEnableHyperlinkAuditing,
       true,
       user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
+  registry->RegisterListPref(
+      prefs::kWebKitEnableDeprecatedFeatures,
+      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
 }
 
 // static
@@ -2381,6 +2384,23 @@ void ChromeContentBrowserClient::OverrideWebkitPrefs(
           extension, view_type, web_prefs);
     }
   }
+
+  // Set list of deprecated features to enable.
+  web_prefs->deprecated_features_to_enable.clear();
+  web_prefs->deprecated_features_to_enable.resize(
+      webkit_glue::DEPRECATED_FEATURE_COUNT, false);
+  const base::ListValue* deprecated_features_list =
+      prefs->GetList(prefs::kWebKitEnableDeprecatedFeatures);
+  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 < webkit_glue::DEPRECATED_FEATURE_COUNT) {
+      web_prefs->deprecated_features_to_enable[value] = true;

[jamesr, 2014/06/10 18:11:27]

I understand you're in a hurry to land but this is a crazy amount of code to add
to pipe a single boolean value through.  I'm guessing this is why our size graph
looks like this:

https://chromeperf.appspot.com/report?tests=sizes%2Fchrome&masters=Chromium&b...

Do we really need a generalized mechanism here?  What else do we expect to use
this functionality?

[Andrew T Wilson (Slow), 2014/06/10 18:53:33]

The goal is that many future deprecated APIs would have associated policy flags
to temporarily extend their life for enterprise users. So a more general policy
framework is required so we don't have to re-roll individual booleans for every
API.

Agreed that this is overkill if we never have another deprecated API that we
want to extend the life, but already we've had a few requests for this and we
expect this to be an ongoing issue.

+    }
+  }
 }
 
 void ChromeContentBrowserClient::UpdateInspectorSetting(