Merge commit 'android-4.2.1_r1' into Upgrade_branch
* commit 'android-4.2.1_r1':
hwc: don't open sysfs on every iteration
hwc/overlay: Add premultiplied alpha support.
hwc: external: Cleanup overlay objects on external disconnect.
display/libhwcomposer: fix potential memory leak
hwc: Skip secure buffers in non secure mode
hwc: move enable disable ioctls to vsync thread
hwc: fix some race conditions
don't call vsync-ctrl ioctl for same enable value
hwc: Close unused pipes before PAN
hwc: Call sync before draw.
hwc: Fix tearing on HDMI. Call glFinish()
hwc: Check for the validity of the fb layer
hwc: Fix dpi values reported
liboverlay: close all the opened pipes after framework reboot.
hwc: Add non-zero checks. Move warning log.
libgralloc: remove pid checks