Object-based DisplayList recording

bug:8037003

Changes the DisplayList from using stream read/write commands to use an array of
objects manually allocated on a linear buffer.

Depends on frameworks/native change https://googleplex-android-review.googlesource.com/#/c/257695/ which adds LinearAllocator

Also changes drawRects to use float count instead of rect count, to be more like drawLines/drawPoints

Change-Id: Ia2e4a11acd8f0a757042a05cbc9e7563cb73ee47