Style guide: Attempt to make the L2 and L3 headings more visually distinct
Style guide: Attempt to make the L2 and L3 headings more visually distinct

The default style of the L2 and L3 headers are too similar, making it difficult to see which is which.

BUG=none
NOTRY=true

Change-Id: I0deede2ad5766db9b63baa48be8e4da4aba784ca
Reviewed-on: https://chromium-review.googlesource.com/657697
Commit-Queue: Karl Wiberg <2c708eb0a58047bf403399f50b3da33ffd2dd444@webrtc.org>
Reviewed-by: Danil Chapovalov <55de8d9c2b5977da2dd48f967f21f9d606b172a5@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#19759}
TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc