[Android] Provider a native (C++) MotionEvent wrapper

Rather than using custom Java and C++ classes for translating MotionEvent
data into a format expected by content/, provider a proper wrapper of the
MotionEvent class.  This exposes additional event data necessary for the unified
C++ port of Android's gesture detection framework.  It also eliminates
TouchPoint array garbage generated each time a MotionEvent is sent to native.

BUG=332418
TBR=avi@chromium.org

Review URL: https://codereview.chromium.org/149463003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248283 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248283