Fix windows compile error

Author: liyuqian

shell/common/input_events_unittests.cc

@@ -8,6 +8,8 @@
 namespace flutter {
 namespace testing {
 
+#ifdef OS_MACOSX || OS_LINUX  // the following tests only work on linux or mac
+
 using Generator = std::function<int(int)>;
 
 TEST_F(ShellTest, MissAtMostOneFrameForIrregularInputEvents) {
@@ -112,5 +114,7 @@ TEST_F(ShellTest, HandlesActualIphoneXsInputEvents) {
   }
 }
 
+#endif  // OS_MACOXS || OS_LINUX
+
 }  // namespace testing
 }  // namespace flutter