b/3307761 Tuning two fingers pan.
b/3307761 Tuning two fingers pan.

User reports jumpy when trying two fingers pan. This change keeps
track of the previous movements of the fingers' middle point,
compares to the change of the fingers' distance, and decides
to pan or zoom or do both.

Change-Id: I8a6a8e9259db85b0e820b6e25ba0822ed289fb45

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