cc: Add LayerTreeHost::InitParams for LayerTreeHost creation.

Instead of passing in a number of things to the LayerTreeHost constructor,
use a struct to simplify the code a bit, and make this more readable. This
also makes it easy to maintain a development branch that adds new things.

TBR=jam@ for API usage update in android_webview/, components/, and content/

BUG=436952

Review URL: https://codereview.chromium.org/1126253005

Cr-Commit-Position: refs/heads/master@{#329164}
19 files changed