Handle invalid contexts in CredentialManager callbacks better.

As of crrev.com/c/536543, it's an error to call ExecutionContext::From()
on an invalid |context|. Update guards in request/notification callbacks
in blink::CredentialsContainer to instead rely on ScriptPromiseResolver
being a ContextLifecycleObserver, which is able to safely return the
Frame (i.e. browsing context) associated with its ExecutionContext (here
always a document) if it is still active, and a nullptr otherwise.

This CL also removes a useless copy of |web_credentials|.

Bug: 794278
Change-Id: Iefe3557dbc374a81964be7f5f51a9f8b73e93e51
Reviewed-on: https://chromium-review.googlesource.com/824267
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524368}

third_party/WebKit/Source/modules/credentialmanager/CredentialsContainer.cpp

@@ -155,9 +155,7 @@ class NotificationCallbacks
   ~NotificationCallbacks() override {}
 
   void OnSuccess() override {
-    Frame* frame =
-        ToDocument(ExecutionContext::From(resolver_->GetScriptState()))
-            ->GetFrame();
+    Frame* frame = resolver_->GetFrame();
     SECURITY_CHECK(!frame ||
                    same_origin_requirement_ ==
                        SameOriginRequirement::kCanBeCrossOrigin ||
@@ -183,16 +181,10 @@ class RequestCallbacks : public WebCredentialManagerClient::RequestCallbacks {
       : resolver_(resolver) {}
   ~RequestCallbacks() override {}
 
-  void OnSuccess(std::unique_ptr<WebCredential> web_credential) override {
-    ExecutionContext* context =
-        ExecutionContext::From(resolver_->GetScriptState());
-    if (!context)
-      return;
-    Frame* frame = ToDocument(context)->GetFrame();
+  void OnSuccess(std::unique_ptr<WebCredential> credential) override {
+    Frame* frame = resolver_->GetFrame();
     SECURITY_CHECK(!frame || IsSameOriginWithAncestors(frame));
 
-    std::unique_ptr<WebCredential> credential =
-        WTF::WrapUnique(web_credential.release());
     if (!frame) {
       resolver_->Resolve();
       return;
@@ -235,11 +227,7 @@ class PublicKeyCallbacks : public WebAuthenticationClient::PublicKeyCallbacks {
 
   void OnSuccess(
       webauth::mojom::blink::PublicKeyCredentialInfoPtr credential) override {
-    ExecutionContext* context =
-        ExecutionContext::From(resolver_->GetScriptState());
-    if (!context)
-      return;
-    Frame* frame = ToDocument(context)->GetFrame();
+    Frame* frame = resolver_->GetFrame();
     SECURITY_CHECK(!frame || frame == frame->Tree().Top());
 
     if (!frame) {

third_party/WebKit/Source/modules/credentialmanager/CredentialsContainerTest.cpp

@@ -45,8 +45,9 @@ TEST(CredentialsContainerTest, TestGetWithDocumentDestroyed) {
   CredentialsContainer* credential_container = CredentialsContainer::Create();
   std::unique_ptr<WebCredentialManagerClient::RequestCallbacks> get_callback;
 
-  V8TestingScope scope;
   {
+    V8TestingScope scope;
+
     // Set up.
     scope.GetDocument().SetSecurityOrigin(
         SecurityOrigin::CreateFromString("https://example.test"));