GC triggering performance optimizations

Copy the correct starting heap size at process init.
Interfaces to set GC/managed heap parameters.

Change-Id: Ia2b158aa28254d88f68c9534a0eef580aa811b10
Configure dalvik heap parameters for low memory devices

Reduces after boot memory footprint by about 5-8MB
Note: This is for low memory based devices only (~512MB RAM
or less)

Change-Id: I4b4b9ae3efaff96551457e566bbb9bd4f0f23fd5
build/phone-xhdpi-1024-dalvik-heap.mk Revert AOSP heapgrowthlimit change from 64 to 96

This reverts part of AOSP change at

https://android.googlesource.com/platform/frameworks/native/+/c84e9844d621223d14178be521

Possible performance issues have arisen because of it. Discussion at

http://code.google.com/p/android/issues/detail?id=40961

Patch Set 2: Clean up commit message

Change-Id: Id7e3324607f92553a98e4d47da58a322e4fba657
Add heap configuration for 1080p phones with 2048m

 * Increase heap start size to 16m to minimize GC with larger bitmaps

Change-Id: I8fbba2e5a2a2cf2d7a6898ca6bae8639d6cf5a19
provide overrides for hwui memory limits for xxhdpi phones

Change-Id: I8b369619cd07530d0468a5449da30f338c13c7d2