Mark JSONEncoder::Emit as inline

This speeds up serialization of messages with very large strings. E.g an
inspector-protocol test case with a very large script by ~5-~10%.

Before: https://pprofng.corp.google.com/?id=f8b1f0579d5f366710da1107ddd9cd05&tab=flame&source=cli

After: https://pprofng.corp.google.com/?id=68628e63a993b60db52417849fdd3f10&tab=flame&source=cli

Note that in the flamegraph JSONEncoder::Emit was folded together with
SnapshoteByteSink::Put due to LTO.

R=caseq@chromium.org

Bug: 326554286
Change-Id: I1a287f32214da670eae1a2b6880dac7bbcbc38eb
1 file changed