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 e83e981f76ec2610cbf3af28510fea87ca16431e..273f1259e45670b82672b9cc4c7ea4cd0ebed08b 100644
--- a/chrome/browser/policy/policy_browsertest.cc
+++ b/chrome/browser/policy/policy_browsertest.cc
@@ -705,7 +705,8 @@ class PolicyTest : public InProcessBrowserTest {
         expect_success ? chrome::NOTIFICATION_EXTENSION_UNINSTALLED_DEPRECATED
                        : chrome::NOTIFICATION_EXTENSION_UNINSTALL_NOT_ALLOWED,
         content::NotificationService::AllSources());
-    extension_service()->UninstallExtension(id, false, NULL);
+    extension_service()->UninstallExtension(
+        id, ExtensionService::UNINSTALL_REASON_DEFAULT, NULL);
     observer.Wait();
   }