No real functional change, but instead of lazy-loading AVFoundation, it's
now linked like all the other system frameworks and loaded by the dynamic
linker at program startup.  While unlikely, this might have an effect
on startup time.

BUG=579648
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2529493002
Cr-Commit-Position: refs/heads/master@{#434776}