Remove the migration code from content_settings::DefaultProvider.

The migration of default content settings from one dictionary pref into individual prefs appeared in M43. The next branchpoint is M46. After three versions, it is safe to remove the migration code.

Question: What happens to users who weren't migrated during this time (i.e. jump from M<43 to M>=46)?
Answer: Their content settings will be reset, since their individual prefs will not be populated. However, their profile won't be damaged; the old dictionary will be simply ignored. Thus, the user will have their settings restored to default values, as if in a new profile. For the more sensitive settings, the user will be asked before a permission is granted to the site; however, for cookies, images and javascript the default value is to allow websites to use them.

TESTED=Change in the settings UI was correctly reflected in the same window, in incognito window, and for synced settings also on a synced computer.

BUG=452388

Review URL: https://codereview.chromium.org/1252973002

Cr-Commit-Position: refs/heads/master@{#340475}

1 files changed, 2 insertions, 4 deletions

diff --git a/chrome/browser/prefs/pref_functional_browsertest.cc b/chrome/browser/prefs/pref_functional_browsertest.cc
index 0a9331a..642d9fa 100644
--- a/chrome/browser/prefs/pref_functional_browsertest.cc
+++ b/chrome/browser/prefs/pref_functional_browsertest.cc
@@ -87,10 +87,8 @@ IN_PROC_BROWSER_TEST_F(PrefsFunctionalTest, TestImageContentSettings) {
       &result));
   EXPECT_TRUE(result);
 
-  base::DictionaryValue value;
-  value.SetInteger("images", 2);
-  browser()->profile()->GetPrefs()->Set(prefs::kDefaultContentSettings,
-                                        value);
+  browser()->profile()->GetPrefs()->SetInteger(
+      prefs::kDefaultImagesSetting, CONTENT_SETTING_BLOCK);
 
   ui_test_utils::NavigateToURL(
       browser(),