whether implicit trusts such as for example Google Play Licensing[1] or explicit trusts such as for example the set of Certification Authorities Android devices ship with, you are trusting Google in many ways.

[1] https://support.google.com/googleplay/android-developer/answ...

In the example you provide, you are trusting google in the same way you are trusting every SSL cert authority. What you are responding to is a reference to the signing of the APK, which is not (and cannot be) done by google even if the security of the transport layer is compromised.