Merge "Upgrade libpng to v1.6.40" am: 27bd9cf3d0 am: 6f2b0d3a5f am: edfff8897e am: b936c177bb am: af839e6640 am: 7442ebec21

Original change: https://android-review.googlesource.com/c/platform/external/libpng/+/2636112

Change-Id: I9a64f396b21cdad02406c0e3c129001113bda8fa
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>