Replace "external_install" boolean parameter with explicit enumeration in ExtensionUninstall method.

chrome/browser/policy/policy_browsertest.cc

Index: chrome/browser/policy/policy_browsertest.cc
diff --git a/chrome/browser/policy/policy_browsertest.cc b/chrome/browser/policy/policy_browsertest.cc
index 53bbac941f397bae0abf484ae12d488fcf6e0762..0de12a062651c8e4dd015641227e3a0f04ae1cb1 100644
--- a/chrome/browser/policy/policy_browsertest.cc
+++ b/chrome/browser/policy/policy_browsertest.cc
@@ -712,7 +712,8 @@ class PolicyTest : public InProcessBrowserTest {
         expect_success ? chrome::NOTIFICATION_EXTENSION_UNINSTALLED
                        : chrome::NOTIFICATION_EXTENSION_UNINSTALL_NOT_ALLOWED,
         content::NotificationService::AllSources());
-    extension_service()->UninstallExtension(id, false, NULL);
+    extension_service()->UninstallExtension(
+        id, ExtensionService::kUninstallReasonDefault, NULL);
     observer.Wait();
   }