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The client will use GRPC to talk to cast_shell to create and manage
webviews. One RPC corresponds to a given webview and input and
commands and send over this channel. Presentation is handled by
wayland/exo and associating a wayland surface with a webview

TEST=local test w/ desktop cast_shell & wayland_fullscreen_client
BUG=b/132811925

Change-Id: I8f0da747805973174c46f1d824758c6c2ee04674
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1678288
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
Reviewed-by: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678456}