Add a function to query the available memory on the device.
Add a function to query the available memory on the device.

This function is called over JNI to determine wheter a particular
size of memory allocation will leave us in a low memory state.

Bug: 5142892
Change-Id: I3d0f85075497c2a374cd866b0223eecaaa4b5f46

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base