Add getHashChain() to IBase.

Each interface has a getHashChain() method that
returns the hash of all .hal files from the rtti
of the interface up to IBase.

Test: hidl_test

Bug: 36602587
Change-Id: I13f2e54bd45593c70064dff05fa934d5cd01996a
diff --git a/Interface.h b/Interface.h
index 1b3ebb5..793226a 100644
--- a/Interface.h
+++ b/Interface.h
@@ -117,6 +117,7 @@
     bool fillPingMethod(Method *method) const;
     bool fillDescriptorChainMethod(Method *method) const;
     bool fillGetDescriptorMethod(Method *method) const;
+    bool fillHashChainMethod(Method *method) const;
     bool fillSyspropsChangedMethod(Method *method) const;
     bool fillLinkToDeathMethod(Method *method) const;
     bool fillUnlinkToDeathMethod(Method *method) const;