Stop inheriting push notification permissions from regular to incognito

components/content_settings/core/browser/content_settings_default_provider.cc

Index: components/content_settings/core/browser/content_settings_default_provider.cc
diff --git a/components/content_settings/core/browser/content_settings_default_provider.cc b/components/content_settings/core/browser/content_settings_default_provider.cc
index 90531a5795644596733a9027d393632c012f93c5..40c1ed491c2cf932dabb36daa06f2ec0a3e0ac1e 100644
--- a/components/content_settings/core/browser/content_settings_default_provider.cc
+++ b/components/content_settings/core/browser/content_settings_default_provider.cc
@@ -260,6 +260,10 @@ scoped_ptr<RuleIterator> DefaultProvider::GetRuleIterator(
     ContentSettingsType content_type,
     const ResourceIdentifier& resource_identifier,
     bool incognito) const {
+  // The default provider never has incognito-specific settings.

[msramek, 2015/11/27 16:30:04]

This is wrong, please remove it.

With this change, when HostContentSettingsMap asks DefaultProvider what is the
default setting for incognito, it will respond "I don't know", and
HostContentSettingsMap will use CONTENT_SETTING_DEFAULT.

That is incorrect. The setting set by DefaultProvider (i.e. what you see in the
radio groups in chrome://settings/content) is valid for both the regular and
incognito mode (which is exactly why the incognito parameter is ignored here).

[johnme, 2015/11/30 14:56:58]

I think this is actually correct. GetRuleIterator is only called from three
places:
1. HostContentSettingsMap::GetDefaultContentSettingFromProvider
2. GetContentSettingValueAndPatterns (content_settings_utils.cc)
3. HostContentSettingsMap::AddSettingsForOneType, which is in turn only called
by HostContentSettingsMap::GetSettingsForOneType.

Of these, #1 only ever passes false for |incognito| (so this change has no
effect), and both #2 and #3 either only pass false, or pass true immediately
followed by false. In the latter case, it'll still correctly inherit the default
setting into incognito.

And semantically, this change aligns DefaultProvider with the comment on
ProviderInterface::GetRuleIterator, which says "If |incognito| is true, the
iterator returns only the content settings which are applicable to the incognito
mode and differ from the normal mode. Otherwise, it returns the content settings
for the normal mode."

[msramek, 2015/12/01 13:41:43]

Ahhh! Somehow I have never noticed this; I have always been thinking of this
method as returning the same settings for regular mode and incognito. But for
incognito, it should really only return the incognito-*specific* settings, which
there are none.

This change is a no-op due to the way how we use the iterator, but you're right
that only now is it consistent with the description, so I agree that this is a
positive change :-)

[johnme, 2015/12/02 15:13:16]

Acknowledged.

+  if (incognito)
+    return scoped_ptr<RuleIterator>(new EmptyRuleIterator());
+
   base::AutoLock lock(lock_);
   if (resource_identifier.empty()) {
     auto it(default_settings_.find(content_type));