Make TimestampedValue Parcelable for simplicity.
TimetampedValue objects are not generally parcelable, depending on the
type of the value held. Previously, TimestampedValue did not implement
Parcelable to avoid committing to a general contract. Developers
parceling TimestampedValue objects were expected to call
TimestampedValue.writeToParcel() / TimestampedValue.readFromParcel()
explicitly when they knew it was safe to do so. This also meant that
TimestampedValues couldn't be used directly via AIDL.
This change makes TimestampedValue parcelable because it's more
familiar / convenient. Attempts to marshall a TimestampedValue that
contains a non-parcelable value will still throw a RuntimeException.
Bug: 140712361
Test: atest android.util.TimestampedValueTest
Change-Id: I8ca9c72f0433b380ce720cd813f650e743b3ddae
def77b5cd5