Skip mulitple-dispay tests on win8

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index 2d9f71707e19fbf226bc539d7014c9f355ef8520..53c2e50467c5d7d254fb8a3439ae196086ca5d1e 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -95,6 +95,10 @@ class AshTestBase : public testing::Test {
   aura::test::EventGenerator& GetEventGenerator();
 
  protected:
+  // True if the running environment supports multiple displays,
+  // or false otherwise (e.g. win8 bot).
+  static bool SupportsMultipleDisplays();
+
   void RunAllPendingInMessageLoop();
 
   // Utility methods to emulate user logged in or not, session started or not