Add a global on/off switch for content settings and expose a toggle on the Website Settings options…

chrome/browser/content_settings/content_settings_override_provider.h

Index: chrome/browser/content_settings/content_settings_override_provider.h
diff --git a/chrome/browser/content_settings/content_settings_override_provider.h b/chrome/browser/content_settings/content_settings_override_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..babbdc3b97c85c374cca947e35107a6e3f1954fc
--- /dev/null
+++ b/chrome/browser/content_settings/content_settings_override_provider.h
@@ -0,0 +1,57 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.

[Bernhard Bauer, 2014/09/10 09:07:18]

2014, and I think the (c) shouldn't be there for new files.

[Daniel Nishi, 2014/09/10 16:38:29]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OVERRIDE_PROVIDER_H_
+#define CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OVERRIDE_PROVIDER_H_
+
+#include <map>
+
+#include "base/basictypes.h"

[Bernhard Bauer, 2014/09/10 09:07:17]

Do you actually need basictypes here, or base/macros.h (for
DISALLOW_COPY_AND_ASSIGN)?

[Daniel Nishi, 2014/09/10 16:38:29]

The latter.

Done.

+#include "base/synchronization/lock.h"
+#include "components/content_settings/core/common/content_settings_types.h"
+
+class PrefService;
+
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
+namespace content_settings {
+
+// OverrideProvider contains if certain content settings are enabled or
+// globally disabled.

[Bernhard Bauer, 2014/09/10 09:07:18]

What's the thread safety story here?

[Daniel Nishi, 2014/09/10 16:38:29]

I think now that I've locked checking IsEnabled(), the locks should keep the
thread safety for IsEnabled() and SetContentSetting().

+class OverrideProvider {
+ public:
+  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
+
+  OverrideProvider(PrefService* prefs, bool incognito);
+  virtual ~OverrideProvider();
+
+  // Returns if |content_type| is enabled.

[Bernhard Bauer, 2014/09/10 09:07:17]

Note that content settings in principle are a general map, and not every content
type necessarily has a "disabled" setting. I think you ran into that with media
stream.

If we keep this interface (see my comment in the .cc file), we should make it
clearer what enabled and disabled means (i.e. enabled means look at other
content settings and return whatever setting is stored there, disabled means
forcing the setting to a disabled value, whatever that is for the content type
at hand).

[Daniel Nishi, 2014/09/10 16:38:29]

I've clarified the comment.

I think for how it is currently exposed, we should be fine. It'd be a bit dicier
if something like handlers or zoom was exposed as being globally blocked, but I
think our current set shouldn't bring up too many problems.

+  bool IsEnabled(ContentSettingsType content_type) const;
+
+  // Sets |content_type|'s enabled status.
+  void SetContentSetting(ContentSettingsType content_type, bool is_enabled);
+
+ private:
+  // Reads the override settings from the preferences service.
+  void ReadOverrideSettings();
+
+  // Copies of the pref data, so that we can read it on the IO thread.
+  std::map<ContentSettingsType, bool> override_settings_;
+
+  PrefService* prefs_;
+
+  bool is_incognito_;
+
+  // Used around accesses to the |override_content_settings_| object to
+  // guarantee thread safety.
+  mutable base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverrideProvider);
+};
+
+}  // namespace content_settings
+
+#endif  // CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OVERRIDE_PROVIDER_H_