Use nullptr instead of reinterpret_cast of NULL to pointer type am: d524f97614 am: e079d61912 am: e9ddf7d93d am: 4fd8f6d047

Original change: https://android-review.googlesource.com/c/platform/external/libchrome/+/1972019

Change-Id: Ifabfd4aa1e83ca18b6f788aa2b86a8651d21784d