Restore thread check in KeyedService factories.

components/keyed_service/content/browser_context_keyed_base_factory.cc

Index: components/keyed_service/content/browser_context_keyed_base_factory.cc
diff --git a/components/keyed_service/content/browser_context_keyed_base_factory.cc b/components/keyed_service/content/browser_context_keyed_base_factory.cc
index 7c2d8b797c54c8592e6685996e1bb26ec5e710d4..7e3ab94e069f33537e9c020ce287562c7e90c520 100644
--- a/components/keyed_service/content/browser_context_keyed_base_factory.cc
+++ b/components/keyed_service/content/browser_context_keyed_base_factory.cc
@@ -18,9 +18,6 @@ BrowserContextKeyedBaseFactory::~BrowserContextKeyedBaseFactory() {
 
 content::BrowserContext* BrowserContextKeyedBaseFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
-  // TODO(crbug.com/701326): This DCHECK should be moved to GetContextToUse().
-  DCHECK(CalledOnValidThread());
-
   // Safe default for the Incognito mode: no service.
   if (context->IsOffTheRecord())
     return NULL;
@@ -49,6 +46,7 @@ void BrowserContextKeyedBaseFactory::BrowserContextDestroyed(
 
 base::SupportsUserData* BrowserContextKeyedBaseFactory::GetContextToUse(
     base::SupportsUserData* context) const {
+  DCHECK(CalledOnValidThread());
   AssertContextWasntDestroyed(context);
   return GetBrowserContextToUse(static_cast<content::BrowserContext*>(context));
 }