Merge "Matroskaextractor: improve findThumbnails() time." into main am: faa2065048 am: d17d442172

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

Change-Id: I937d17a36fd61dc683b3d549a68f54f4ec238b20
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>