Settings WebUI: Log error in C++ backend when crostini unshare path fails.

Bug: 907256
Change-Id: If223956a330497b4b0318f91e4ea6c941d94b5aa
Reviewed-on: https://chromium-review.googlesource.com/c/1345377
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609890}

chrome/browser/ui/webui/settings/chromeos/crostini_handler.cc

@@ -78,7 +78,14 @@ void CrostiniHandler::HandleRemoveCrostiniSharedPath(
 
   crostini::CrostiniSharePath::GetForProfile(profile_)->UnsharePath(
       crostini::kCrostiniDefaultVmName, base::FilePath(path),
-      base::DoNothing());
+      base::BindOnce(
+          [](const std::string& path, bool result, std::string failure_reason) {
+            if (!result) {
+              LOG(ERROR) << "Error unsharing " << path << ": "
+                         << failure_reason;
+            }
+          },
+          path));
 }
 
 }  // namespace settings