Restore KeyedServiceFactory diagnostics for context use-after-destroy.

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 fe461ffb8f076eedac08a3d9db6c94048cd6b16a..7c2d8b797c54c8592e6685996e1bb26ec5e710d4 100644
--- a/components/keyed_service/content/browser_context_keyed_base_factory.cc
+++ b/components/keyed_service/content/browser_context_keyed_base_factory.cc
@@ -18,12 +18,9 @@ BrowserContextKeyedBaseFactory::~BrowserContextKeyedBaseFactory() {
 
 content::BrowserContext* BrowserContextKeyedBaseFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
+  // TODO(crbug.com/701326): This DCHECK should be moved to GetContextToUse().
   DCHECK(CalledOnValidThread());
 
-#ifndef NDEBUG
-  AssertContextWasntDestroyed(context);

[Paweł Hajdan Jr., 2017/03/21 13:03:24]

Why do we remove this assertion?

[sense (YandexTeam), 2017/03/22 07:38:21]

All this assertions from GetBrowserContextToUse() was moved to GetContextToUse()
(not removed). Why? Because GetBrowserContextToUse() is publicly overridable
method and it's almost always overriden by factories with something like that:
return chrome::GetBrowserContextRedirectedInIncognito(context);
thus the assertion and DCHECK(CalledOnValidThread()) is not called at all.
GetContextToUse() on the other hand is private and marked as final in all base
browser service factories (BrowserContextKeyedBaseFactory,
BrowserContextKeyedServiceFactory, RefcountedBrowserContextKeyedServiceFactory),
so it's always called and cannot be overriden by the user code.

The service construction/getting goes like this:
GetServiceForContext()->GetContextToUse()->GetBrowserContextToUse().

-#endif
-
   // Safe default for the Incognito mode: no service.
   if (context->IsOffTheRecord())
     return NULL;
@@ -52,6 +49,7 @@ void BrowserContextKeyedBaseFactory::BrowserContextDestroyed(
 
 base::SupportsUserData* BrowserContextKeyedBaseFactory::GetContextToUse(
     base::SupportsUserData* context) const {
+  AssertContextWasntDestroyed(context);
   return GetBrowserContextToUse(static_cast<content::BrowserContext*>(context));
 }