Reenable ExtensionWebRequestApiTest.WebRequestBlocking after fixing the flakyness

chrome/browser/extensions/extension_webrequest_apitest.cc

Index: chrome/browser/extensions/extension_webrequest_apitest.cc
diff --git a/chrome/browser/extensions/extension_webrequest_apitest.cc b/chrome/browser/extensions/extension_webrequest_apitest.cc
index 82b0d7fe528db8d68dfbc210d674dfcbd256b3ed..fc2aa0af76fa7e78be4483889a3ea27c9bc04d49 100644
--- a/chrome/browser/extensions/extension_webrequest_apitest.cc
+++ b/chrome/browser/extensions/extension_webrequest_apitest.cc
@@ -90,9 +90,8 @@ IN_PROC_BROWSER_TEST_F(ExtensionWebRequestApiTest, WebRequestAuthRequired) {
       message_;
 }
 
-// Hangs flakily: http://crbug.com/91715
 IN_PROC_BROWSER_TEST_F(ExtensionWebRequestApiTest,
-                       DISABLED_WebRequestBlocking) {
+                       WebRequestBlocking) {
   CommandLine::ForCurrentProcess()->AppendSwitch(
       switches::kEnableExperimentalExtensionApis);