Ensure that IdentityTestEnvironment use the correct PO2TS

IdentityTestEnvironment's method casts the PO2TS to a FakePO2TS
but do not enforce this at compilation (in order to support
IdentityTestEnvironmentProfileAdaptor).

Add a DCHECK in IdentityTestEnvironment::Initialize() to check
that the PO2TS is a FakeProfileOAuth2TokenService (required to
add a new virtual method to determine this as Chromium builds
without RTTI).

Bug: 982751
Change-Id: I151a3e63f22b941d6be40151bba2e453e43be43c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1795602
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697961}

components/signin/internal/identity_manager/fake_profile_oauth2_token_service.cc

@@ -99,3 +99,8 @@ FakeOAuth2AccessTokenManager*
 FakeProfileOAuth2TokenService::GetFakeAccessTokenManager() {
   return static_cast<FakeOAuth2AccessTokenManager*>(GetAccessTokenManager());
 }
+
+bool FakeProfileOAuth2TokenService::IsFakeProfileOAuth2TokenServiceForTesting()
+    const {
+  return true;
+}

components/signin/internal/identity_manager/fake_profile_oauth2_token_service.h

@@ -81,6 +81,8 @@ class FakeProfileOAuth2TokenService : public ProfileOAuth2TokenService {
 
   void set_auto_post_fetch_response_on_message_loop(bool auto_post_response);
 
+  bool IsFakeProfileOAuth2TokenServiceForTesting() const override;
+
  private:
   FakeOAuth2AccessTokenManager* GetFakeAccessTokenManager();
 

components/signin/internal/identity_manager/profile_oauth2_token_service.cc

@@ -355,6 +355,11 @@ void ProfileOAuth2TokenService::OverrideAccessTokenManagerForTesting(
   token_manager_ = std::move(token_manager);
 }
 
+bool ProfileOAuth2TokenService::IsFakeProfileOAuth2TokenServiceForTesting()
+    const {
+  return false;
+}
+
 OAuth2AccessTokenManager* ProfileOAuth2TokenService::GetAccessTokenManager() {
   return token_manager_.get();
 }

components/signin/internal/identity_manager/profile_oauth2_token_service.h

@@ -257,6 +257,8 @@ class ProfileOAuth2TokenService : public OAuth2AccessTokenManager::Delegate,
   void OverrideAccessTokenManagerForTesting(
       std::unique_ptr<OAuth2AccessTokenManager> token_manager);
 
+  virtual bool IsFakeProfileOAuth2TokenServiceForTesting() const;
+
  protected:
   OAuth2AccessTokenManager* GetAccessTokenManager();
 

components/signin/public/identity_manager/identity_test_environment.cc

@@ -128,6 +128,11 @@ void IdentityTestEnvironment::Initialize() {
          "If your test has an existing one, move it to be initialized before "
          "IdentityTestEnvironment. Otherwise, use "
          "base::test::TaskEnvironment.";
+  DCHECK(identity_manager()
+             ->GetTokenService()
+             ->IsFakeProfileOAuth2TokenServiceForTesting())
+      << "IdentityTestEnvironment requires the ProfileOAuth2TokenService used "
+         "to subclass FakeProfileOAuth2TokenServiceForTesting.";
   test_identity_manager_observer_ =
       std::make_unique<TestIdentityManagerObserver>(this->identity_manager());
   this->identity_manager()->AddDiagnosticsObserver(this);