Revert of Unload the ScopedGaiaAuthExtension asynchronously. (patchset #2...

Revert of Unload the ScopedGaiaAuthExtension asynchronously. (patchset #2 id:20001 of https://codereview.chromium.org/961443003/)

Reason for revert:
Broke BookmarkSyncPromoControllerTest.SignInLink on Mac ASan 64: https://build.chromium.org/p/chromium.memory/builders/Mac%20ASan%2064%20Tests%20%281%29/builds/7363

Original issue's description:
> Unload the ScopedGaiaAuthExtension asynchronously.
>
> If we don't do this, then we have a race condition between unloading
> this extension, and trying to use it because we have manually
> navigated to it.
>
> BUG=460431
>
> Committed: https://crrev.com/1805c4c5c4b5292cca51a54f379cde498db7238b
> Cr-Commit-Position: refs/heads/master@{#318140}

TBR=xiyuan@chromium.org,noms@google.com,noms@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=460431

Review URL: https://codereview.chromium.org/944923007

Cr-Commit-Position: refs/heads/master@{#318176}

chrome/browser/extensions/signin/scoped_gaia_auth_extension.cc

@@ -4,10 +4,6 @@
 
 #include "chrome/browser/extensions/signin/scoped_gaia_auth_extension.h"
 
-#include "base/bind.h"
-#include "base/location.h"
-#include "base/single_thread_task_runner.h"
-#include "base/thread_task_runner_handle.h"
 #include "chrome/browser/extensions/signin/gaia_auth_extension_loader.h"
 #include "content/public/browser/browser_context.h"
 
@@ -23,15 +19,6 @@ ScopedGaiaAuthExtension::ScopedGaiaAuthExtension(
 ScopedGaiaAuthExtension::~ScopedGaiaAuthExtension() {
   extensions::GaiaAuthExtensionLoader* loader =
       extensions::GaiaAuthExtensionLoader::Get(browser_context_);
-  if (loader) {
-    // Post this instead of calling it directly, to ensure that the
-    // RenderFrameHost is not used after being destroyed. This would happen,
-    // for example, if we tried to manually navigate to the extension while
-    // the <webview> containing the Gaia sign in page (and therefore the
-    // extension) was the active tab. See crbug.com/460431.
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
-        FROM_HERE,
-        base::Bind(&extensions::GaiaAuthExtensionLoader::UnloadIfNeeded,
-                   base::Unretained(loader)));
-  }
+  if (loader)
+    loader->UnloadIfNeeded();
 }