Various NTPSnippetsService cleanups:

components/ntp_snippets/ntp_snippets_service.cc

Index: components/ntp_snippets/ntp_snippets_service.cc
diff --git a/components/ntp_snippets/ntp_snippets_service.cc b/components/ntp_snippets/ntp_snippets_service.cc
index 02524508ceca77bf9620436e54bc6604c47ab25e..7d3cfdd3eafde7a339856b40fcf2ceb5b67e9c14 100644
--- a/components/ntp_snippets/ntp_snippets_service.cc
+++ b/components/ntp_snippets/ntp_snippets_service.cc
@@ -126,7 +126,7 @@ std::set<std::string> GetSuggestionsHostsImpl(
 }
 
 std::unique_ptr<base::ListValue> SnippetsToListValue(
-    const NTPSnippetsService::NTPSnippetStorage& snippets) {
+    const NTPSnippet::PtrVector& snippets) {
   std::unique_ptr<base::ListValue> list(new base::ListValue);
   for (const auto& snippet : snippets) {
     std::unique_ptr<base::DictionaryValue> dict = snippet->ToDictionary();
@@ -135,7 +135,7 @@ std::unique_ptr<base::ListValue> SnippetsToListValue(
   return list;
 }
 
-bool ContainsSnippet(const NTPSnippetsService::NTPSnippetStorage& haystack,
+bool ContainsSnippet(const NTPSnippet::PtrVector& haystack,
                      const std::unique_ptr<NTPSnippet>& needle) {
   const std::string& id = needle->id();
   return std::find_if(haystack.begin(), haystack.end(),
@@ -161,7 +161,8 @@ NTPSnippetsService::NTPSnippetsService(
     NTPSnippetsScheduler* scheduler,
     std::unique_ptr<NTPSnippetsFetcher> snippets_fetcher,
     std::unique_ptr<ImageFetcher> image_fetcher)
-    : enabled_(false),
+    : state_(State::NOT_INITED),
+      enabled_(false),
       pref_service_(pref_service),
       suggestions_service_(suggestions_service),
       file_task_runner_(file_task_runner),
@@ -173,7 +174,9 @@ NTPSnippetsService::NTPSnippetsService(
       &NTPSnippetsService::OnFetchFinished, base::Unretained(this)));
 }
 
-NTPSnippetsService::~NTPSnippetsService() {}
+NTPSnippetsService::~NTPSnippetsService() {
+  DCHECK(state_ == State::NOT_INITED || state_ == State::SHUT_DOWN);
+}
 
 // static
 void NTPSnippetsService::RegisterProfilePrefs(PrefRegistrySimple* registry) {
@@ -183,6 +186,9 @@ void NTPSnippetsService::RegisterProfilePrefs(PrefRegistrySimple* registry) {
 }
 
 void NTPSnippetsService::Init(bool enabled) {
+  DCHECK(state_ == State::NOT_INITED);

[Marc Treib, 2016/05/17 11:21:18]

DCHECK_EQ etc don't work with enum class :(
(I guess we could cast everything to int, but at that point it's way less ugly
to just use regular DCHECK IMO.)

[Bernhard Bauer, 2016/05/17 12:38:13]

Yuck. TBH, I'm less and less convinced that enum classes are All That.

Oh, and I guess appending |state_| to the DCHECK to log it doesn't work either,
because operator<< isn't defined, right?

[Marc Treib, 2016/05/17 12:46:34]

Yup, the missing operator<< is the reason DCHECK_EQ doesn't work.
Would you prefer a non-class enum? Or alternatively, it should be possible to
explicitly overload operator<< (and cast to int there). WDYT?

+  state_ = State::INITED;
+
   enabled_ = enabled;
   if (enabled_) {
     // |suggestions_service_| can be null in tests.
@@ -205,8 +211,12 @@ void NTPSnippetsService::Init(bool enabled) {
 }
 
 void NTPSnippetsService::Shutdown() {
+  DCHECK(state_ == State::INITED);
+  state_ = State::SHUT_DOWN;
+
   FOR_EACH_OBSERVER(NTPSnippetsServiceObserver, observers_,
                     NTPSnippetsServiceShutdown());
+  suggestions_service_subscription_.reset();
   enabled_ = false;
 }
 
@@ -350,7 +360,7 @@ void NTPSnippetsService::OnFetchFinished(
   LoadingSnippetsFinished();
 }
 
-void NTPSnippetsService::MergeSnippets(NTPSnippetStorage new_snippets) {
+void NTPSnippetsService::MergeSnippets(NTPSnippet::PtrVector new_snippets) {
   // Remove new snippets that we already have, or that have been discarded.
   new_snippets.erase(
       std::remove_if(new_snippets.begin(), new_snippets.end(),
@@ -400,7 +410,7 @@ void NTPSnippetsService::MergeSnippets(NTPSnippetStorage new_snippets) {
 }
 
 void NTPSnippetsService::LoadSnippetsFromPrefs() {
-  NTPSnippetStorage prefs_snippets;
+  NTPSnippet::PtrVector prefs_snippets;
   bool success = NTPSnippet::AddFromListValue(
       *pref_service_->GetList(prefs::kSnippets), &prefs_snippets);
   DCHECK(success) << "Failed to parse snippets from prefs";