[MERGE #1644 @rajatd] Fix a potential bug in InstallGuards
[MERGE #1644 @rajatd] Fix a potential bug in InstallGuards

Merge pull request #1644 from rajatd:cachedTypes

Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore