Disable ArgumentValidation test, as it crashes on Mac.

chrome/browser/extensions/webstore_startup_installer_browsertest.cc

Index: chrome/browser/extensions/webstore_startup_installer_browsertest.cc
===================================================================
--- chrome/browser/extensions/webstore_startup_installer_browsertest.cc	(revision 188321)
+++ chrome/browser/extensions/webstore_startup_installer_browsertest.cc	(working copy)
@@ -146,7 +146,13 @@
   RunTest("runTest");
 }
 
-IN_PROC_BROWSER_TEST_F(WebstoreStartupInstallerTest, ArgumentValidation) {
+// Crashes at random intervals on MacOS: http://crbug.com/95713.
+#if defined(OS_MACOSX)
+#define Maybe_ArgumentValidation DISABLED_ArgumentValidation
+#else
+#define Maybe_ArgumentValidation ArgumentValidation
+#endif
+IN_PROC_BROWSER_TEST_F(WebstoreStartupInstallerTest, Maybe_ArgumentValidation) {
   CommandLine::ForCurrentProcess()->AppendSwitchASCII(
       switches::kAppsGalleryInstallAutoConfirmForTests, "cancel");