2 files changed, 19 insertions, 7 deletions
diff --git a/chrome/browser/content_settings/host_content_settings_map.cc b/chrome/browser/content_settings/host_content_settings_map.cc
index 14c251d..8749d6f 100644
--- a/chrome/browser/content_settings/host_content_settings_map.cc
+++ b/chrome/browser/content_settings/host_content_settings_map.cc
@@ -79,7 +79,7 @@ HostContentSettingsMap::HostContentSettingsMap(
     PrefService* prefs,
     bool incognito) :
 #ifndef NDEBUG
-      used_content_settings_providers_(false),
+      used_from_thread_id_(base::PlatformThread::CurrentId()),
 #endif
       prefs_(prefs),
       is_off_the_record_(incognito) {
@@ -108,10 +108,6 @@ HostContentSettingsMap::HostContentSettingsMap(
 void HostContentSettingsMap::RegisterExtensionService(
     ExtensionService* extension_service) {
   DCHECK(extension_service);
-  // http://crbug.com/176315
-  // #ifndef NDEBUG
-  //   DCHECK(!used_content_settings_providers_);
-  // #endif
   DCHECK(!content_settings_providers_[INTERNAL_EXTENSION_PROVIDER]);
   DCHECK(!content_settings_providers_[CUSTOM_EXTENSION_PROVIDER]);
 
@@ -129,6 +125,11 @@ void HostContentSettingsMap::RegisterExtensionService(
   content_settings_providers_[CUSTOM_EXTENSION_PROVIDER] =
       custom_extension_provider;
 
+#ifndef NDEBUG
+  DCHECK(used_from_thread_id_ != base::kInvalidThreadId)
+      << "Used from multiple threads before initialization complete.";
+#endif
+
   OnContentSettingChanged(ContentSettingsPattern(),
                           ContentSettingsPattern(),
                           CONTENT_SETTINGS_TYPE_DEFAULT,
@@ -512,7 +513,11 @@ void HostContentSettingsMap::AddSettingsForOneType(
 
 void HostContentSettingsMap::UsedContentSettingsProviders() const {
 #ifndef NDEBUG
-  used_content_settings_providers_ = true;
+  if (used_from_thread_id_ == base::kInvalidThreadId)
+    return;
+
+  if (base::PlatformThread::CurrentId() != used_from_thread_id_)
+    used_from_thread_id_ = base::kInvalidThreadId;
 #endif
 }
 
diff --git a/chrome/browser/content_settings/host_content_settings_map.h b/chrome/browser/content_settings/host_content_settings_map.h
index 46f62ff..1f1637f 100644
--- a/chrome/browser/content_settings/host_content_settings_map.h
+++ b/chrome/browser/content_settings/host_content_settings_map.h
@@ -15,6 +15,7 @@
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/threading/platform_thread.h"
 #include "base/tuple.h"
 #include "chrome/browser/content_settings/content_settings_observer.h"
 #include "chrome/common/content_settings.h"
@@ -236,7 +237,13 @@ class HostContentSettingsMap
   void UsedContentSettingsProviders() const;
 
 #ifndef NDEBUG
-  mutable bool used_content_settings_providers_;
+  // This starts as the thread ID of the thread that constructs this
+  // object, and remains until used by a different thread, at which
+  // point it is set to base::kInvalidThreadId. This allows us to
+  // DCHECK on unsafe usage of content_settings_providers_ (they
+  // should be set up on a single thread, after which they are
+  // immutable).
+  mutable base::PlatformThreadId used_from_thread_id_;
 #endif
 
   // Weak; owned by the Profile.