Ensure AppServiceProxy is present before use in ExecuteWebTask.

The App Service is not present for all profiles (ie. when in Incognito
mode). After requesting it for a profile, ensure we got back a valid
pointer before use.

      Incognito mode. Expect Chrome not to crash. Chrome does not Crash.

Bug: 1111695
Test: Try to launch default app from "File Saved" notification while in
Test: out/Default/browser_tests --gtest-filter="*FilesAppBrowserTest*"
Change-Id: I04a88fc756bcba2898f4b990dc412b58e6df0c63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2360089Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Josh Simmons <simmonsjosh@google.com>
Cr-Commit-Position: refs/heads/master@{#799543}

chrome/browser/chromeos/file_manager/web_file_tasks.cc

@@ -142,6 +142,14 @@ void ExecuteWebTask(Profile* profile,
   for (const auto& file_system_url : file_system_urls)
     launch_files->file_paths.push_back(file_system_url.path());
 
+  // App Service doesn't exist in Incognito mode but apps can be
+  // launched (ie. default handler to open a download from its
+  // notification) from Incognito mode. Use the base profile in these
+  // cases (see crbug.com/1111695).
+  if (profile->IsOffTheRecord()) {
+    profile = profile->GetOriginalProfile();
+  }
+
   apps::AppServiceProxy* proxy =
       apps::AppServiceProxyFactory::GetForProfile(profile);
   proxy->LaunchAppWithFiles(