IBase: add ping method

Add ping method to IBase. We deleted this from libhwbinder types, so
moving it to hidl types.

Bug: 34501346
Test: hidl_test
Change-Id: I1e13a48f1ca3668450def6434650763483baf34e
diff --git a/Interface.h b/Interface.h
index 376a78c..1b3ebb5 100644
--- a/Interface.h
+++ b/Interface.h
@@ -114,6 +114,7 @@
     std::vector<Method *> mUserMethods;
     std::vector<Method *> mReservedMethods;
     mutable bool mIsJavaCompatibleInProgress;
+    bool fillPingMethod(Method *method) const;
     bool fillDescriptorChainMethod(Method *method) const;
     bool fillGetDescriptorMethod(Method *method) const;
     bool fillSyspropsChangedMethod(Method *method) const;