Disable PlatformAppBrowserTest.Messaging on Windows as its flaky.

chrome/browser/apps/app_browsertest.cc

Index: chrome/browser/apps/app_browsertest.cc
diff --git a/chrome/browser/apps/app_browsertest.cc b/chrome/browser/apps/app_browsertest.cc
index 45aac38ebd685fdb2a371668cfe22ba7204f28d0..3121246d3198418ab465782cc5db4f4fada0519a 100644
--- a/chrome/browser/apps/app_browsertest.cc
+++ b/chrome/browser/apps/app_browsertest.cc
@@ -1051,7 +1051,13 @@ IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest, ComponentAppBackgroundPage) {
   ASSERT_TRUE(launched_listener.WaitUntilSatisfied());
 }
 
-IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest, Messaging) {
+// Fails on Win7. http://crbug.com/171450
+#if defined(OS_WIN)
+#define MAYBE_Messaging DISABLED_Messaging
+#else
+#define MAYBE_Messaging Messaging
+#endif
+IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest, MAYBE_Messaging) {
   ExtensionApiTest::ResultCatcher result_catcher;
   LoadAndLaunchPlatformApp("messaging/app2", "Ready");
   LoadAndLaunchPlatformApp("messaging/app1", "Launched");