Eliminate NOTIFICATION_HISTORY_LOADED notification

chrome/browser/predictors/resource_prefetch_predictor.cc

Index: chrome/browser/predictors/resource_prefetch_predictor.cc
diff --git a/chrome/browser/predictors/resource_prefetch_predictor.cc b/chrome/browser/predictors/resource_prefetch_predictor.cc
index 878113d3faa552f34d35eb178acd072970c99778..ea1bd3e1732b0320b9e22f5e247d5911a081b585 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.cc
+++ b/chrome/browser/predictors/resource_prefetch_predictor.cc
@@ -307,7 +307,8 @@ ResourcePrefetchPredictor::ResourcePrefetchPredictor(
       initialization_state_(NOT_INITIALIZED),
       tables_(PredictorDatabaseFactory::GetForProfile(
           profile)->resource_prefetch_tables()),
-      results_map_deleter_(&results_map_) {
+      results_map_deleter_(&results_map_),
+      history_service_observer_(this) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   // Some form of learning has to be enabled.
@@ -325,7 +326,8 @@ void ResourcePrefetchPredictor::RecordURLRequest(
     const URLRequestSummary& request) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (initialization_state_ != INITIALIZED)
-    return;
+    if (!CheckForHistoryService())

[sdefresne, 2014/10/30 17:37:04]

Question: is it really required to insert all those calls to
CheckForHistoryService()? I'm afraid it may be introducing behaviour changes.
Isn't it enough to just call the method from
ResourcePrefetchPredictor::CreateCaches()?

[nshaik, 2014/10/30 21:48:36]

I was trying to be extra careful which I think is needless.
I just realized that StartInitialization is called every time
RecordMainFrameLoadComplete is done.
Changed the code.

+      return;
 
   CHECK_EQ(request.resource_type, content::RESOURCE_TYPE_MAIN_FRAME);
   OnMainFrameRequest(request);
@@ -335,7 +337,8 @@ void ResourcePrefetchPredictor::RecordURLResponse(
     const URLRequestSummary& response) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (initialization_state_ != INITIALIZED)
-    return;
+    if (!CheckForHistoryService())
+      return;
 
   if (response.resource_type == content::RESOURCE_TYPE_MAIN_FRAME)
     OnMainFrameResponse(response);
@@ -347,7 +350,8 @@ void ResourcePrefetchPredictor::RecordURLRedirect(
     const URLRequestSummary& response) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (initialization_state_ != INITIALIZED)
-    return;
+    if (!CheckForHistoryService())
+      return;
 
   CHECK_EQ(response.resource_type, content::RESOURCE_TYPE_MAIN_FRAME);
   OnMainFrameRedirect(response);
@@ -398,15 +402,6 @@ void ResourcePrefetchPredictor::Observe(
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   switch (type) {
-    case chrome::NOTIFICATION_HISTORY_LOADED: {
-      DCHECK_EQ(initialization_state_, INITIALIZING);
-      notification_registrar_.Remove(this,
-                                     chrome::NOTIFICATION_HISTORY_LOADED,
-                                     content::Source<Profile>(profile_));
-      OnHistoryAndCacheLoaded();
-      break;
-    }
-
     case chrome::NOTIFICATION_HISTORY_URLS_DELETED: {
       DCHECK_EQ(initialization_state_, INITIALIZED);
       const content::Details<const history::URLsDeletedDetails>
@@ -461,7 +456,8 @@ void ResourcePrefetchPredictor::OnMainFrameResponse(
     const URLRequestSummary& response) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (initialization_state_ != INITIALIZED)
-    return;
+    if (!CheckForHistoryService())
+      return;
 
   RecordNavigationEvent(NAVIGATION_EVENT_RESPONSE_STARTED);
 
@@ -694,15 +690,7 @@ void ResourcePrefetchPredictor::CreateCaches(
   UMA_HISTOGRAM_COUNTS("ResourcePrefetchPredictor.HostTableHostCount",
                        host_table_cache_->size());
 
-  // Add notifications for history loading if it is not ready.
-  HistoryService* history_service = HistoryServiceFactory::GetForProfile(
-    profile_, Profile::EXPLICIT_ACCESS);
-  if (!history_service) {
-    notification_registrar_.Add(this, chrome::NOTIFICATION_HISTORY_LOADED,
-                                content::Source<Profile>(profile_));
-  } else {
-    OnHistoryAndCacheLoaded();
-  }
+  CheckForHistoryService();
 }
 
 void ResourcePrefetchPredictor::OnHistoryAndCacheLoaded() {
@@ -719,6 +707,7 @@ void ResourcePrefetchPredictor::OnHistoryAndCacheLoaded() {
         this, config_, profile_->GetRequestContext());
   }
 
+  history_service_observer_.RemoveAll();
   initialization_state_ = INITIALIZED;
 }
 
@@ -1221,4 +1210,28 @@ void ResourcePrefetchPredictor::ReportPredictedAccuracyStatsHelper(
 #undef RPP_PREDICTED_HISTOGRAM_COUNTS
 }
 
+bool ResourcePrefetchPredictor::CheckForHistoryService() {
+  if (initialization_state_ == INITIALIZED)
+    return true;
+
+  // Register for HistoryServiceLoading if it is not ready.
+  HistoryService* history_service = HistoryServiceFactory::GetForProfile(
+    profile_, Profile::EXPLICIT_ACCESS);
+  if (history_service && history_service->BackendLoaded()) {
+    // HistoryService is already loaded. Continue with Initialization.
+    OnHistoryAndCacheLoaded();
+    return true;
+  } else if (history_service &&
+      !history_service_observer_.IsObserving(history_service)) {
+    history_service_observer_.Add(history_service);
+  }
+  return false;
+}
+
+void ResourcePrefetchPredictor::OnHistoryServiceLoaded(
+    HistoryService* history_service) {
+  OnHistoryAndCacheLoaded();
+  history_service_observer_.Remove(history_service);
+}
+
 }  // namespace predictors