AccessibilityNodeInfo shouldn't touch extras.

The extras may contain custom Parcelables which aren't in the
system's default classpath, so touching them would end up clobbering
the contents.

Update code to leave the parcelled data untouched inside the bundle
until someone tries reading the extras.

Bug: 27897919
Change-Id: I99381dd50c9a0e8887667076362ea98805f0437c