Merge "Matroskaextractor: improve findThumbnails() time." into main am: faa2065048

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/3019097

Change-Id: Ic97088063203b638745e4544ee97922f24bef45c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>