Reland "Handle unsucessful JsonPrefStore initialization in SupervisedUserSettingsService."

> According to crash reports, it's not very common but still possible for the JsonPrefStore used by SupervisedUserSettingsService to fail initialization (which happens if the profile directory doesn't exist).

Review URL: https://codereview.chromium.org/960233003

This reverts commit 3490af83.

TBR=treib@chromium.org
BUG=463646

Review URL: https://codereview.chromium.org/1016423003

Cr-Commit-Position: refs/heads/master@{#322105}

chrome/browser/supervised_user/supervised_user_settings_service.cc

@@ -50,7 +50,10 @@ bool SettingShouldApplyToPrefs(const std::string& name) {
 }  // namespace
 
 SupervisedUserSettingsService::SupervisedUserSettingsService()
-    : active_(false), local_settings_(new base::DictionaryValue) {}
+    : active_(false),
+      initialization_failed_(false),
+      local_settings_(new base::DictionaryValue) {
+}
 
 SupervisedUserSettingsService::~SupervisedUserSettingsService() {}
 
@@ -97,7 +100,9 @@ void SupervisedUserSettingsService::SetActive(bool active) {
 }
 
 bool SupervisedUserSettingsService::IsReady() {
-  return store_->IsInitializationComplete();
+  // Initialization cannot be complete but have failed at the same time.
+  DCHECK(!(store_->IsInitializationComplete() && initialization_failed_));
+  return initialization_failed_ || store_->IsInitializationComplete();
 }
 
 void SupervisedUserSettingsService::Clear() {
@@ -299,9 +304,16 @@ void SupervisedUserSettingsService::OnPrefValueChanged(const std::string& key) {
 }
 
 void SupervisedUserSettingsService::OnInitializationCompleted(bool success) {
+  if (!success) {
+    // If this happens, it means the profile directory was not found. There is
+    // not much we can do, but the whole profile will probably be useless
+    // anyway. Just mark initialization as failed and continue otherwise,
+    // because subscribers might still expect to be called back.
+    initialization_failed_ = true;
+  }
+
   // TODO(bauerb): Temporary CHECK while investigating https://crbug.com/425785.
   // Remove (or change back to DCHECK) once the bug is fixed.
-  CHECK(success);
   CHECK(IsReady());
   InformSubscribers();
 }
@@ -354,7 +366,7 @@ base::DictionaryValue* SupervisedUserSettingsService::GetDictionaryAndSplitKey(
 
 scoped_ptr<base::DictionaryValue> SupervisedUserSettingsService::GetSettings() {
   DCHECK(IsReady());
-  if (!active_)
+  if (!active_ || initialization_failed_)
     return scoped_ptr<base::DictionaryValue>();
 
   scoped_ptr<base::DictionaryValue> settings(local_settings_->DeepCopy());

chrome/browser/supervised_user/supervised_user_settings_service.h

@@ -152,6 +152,8 @@ class SupervisedUserSettingsService : public KeyedService,
 
   bool active_;
 
+  bool initialization_failed_;
+
   // A set of local settings that are fixed and not configured remotely.
   scoped_ptr<base::DictionaryValue> local_settings_;