[dpwa] Re-enable the web app file handler tests.

Bug: 1270961
Change-Id: Ie6335b64f1d56634d2da67d93bb36659fdacb0fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3572598
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/main@{#989511}

chrome/browser/ui/web_applications/web_app_browsertest.cc

@@ -1913,13 +1913,7 @@ class WebAppBrowserTest_FileHandler : public WebAppBrowserTest {
   base::test::ScopedFeatureList feature_list_;
 };
 
-// TODO(crbug.com/1270961): Flaky on Win and Mac.
-#if BUILDFLAG(IS_WIN) || BUILDFLAG(IS_MAC)
-#define MAYBE_WebAppFileHandler DISABLED_WebAppFileHandler
-#else
-#define MAYBE_WebAppFileHandler WebAppFileHandler
-#endif
-IN_PROC_BROWSER_TEST_F(WebAppBrowserTest_FileHandler, MAYBE_WebAppFileHandler) {
+IN_PROC_BROWSER_TEST_F(WebAppBrowserTest_FileHandler, WebAppFileHandler) {
   os_hooks_suppress_.reset();
   base::ScopedAllowBlockingForTesting allow_blocking;