Don't DCHECK being on the UI thread in failed callback handler.

If a thumbnail request fails because the browser is shutting down. In
that case the failure may be executed after the browser UI thread
is being closed, and the CurrentlyOn(content::BrowserThread::UI)
check will fail.

So move this check to only be executed when the ProcessCapturedBitmap
result is successful, and the function is going to do any work.

R=sky
BUG=270918

Review URL: https://codereview.chromium.org/141273011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245767 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 4 insertions, 1 deletions

diff --git a/chrome/browser/thumbnails/thumbnail_tab_helper.cc b/chrome/browser/thumbnails/thumbnail_tab_helper.cc
index 2e3d47a..17f68f1 100644
--- a/chrome/browser/thumbnails/thumbnail_tab_helper.cc
+++ b/chrome/browser/thumbnails/thumbnail_tab_helper.cc
@@ -66,10 +66,13 @@ void ProcessCapturedBitmap(scoped_refptr<ThumbnailingContext> context,
                            scoped_refptr<ThumbnailingAlgorithm> algorithm,
                            bool succeeded,
                            const SkBitmap& bitmap) {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   if (!succeeded)
     return;
 
+  // On success, we must be on the UI thread (on failure because of shutdown we
+  // are not on the UI thread).
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+
   algorithm->ProcessBitmap(context, base::Bind(&UpdateThumbnail), bitmap);
 }