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Adds the proto definitions to all the remaining Webview calls.
Also implement all the straightforward calls.

TODOs:
 * Javascript message channels,
 * Navigation delegate,
 * Clear cache on the renderer side.

Bug: b/132811925
Test: Compiled
Change-Id: If8cb03e1e26ece586ed841dcdd028a6c5ccf0316
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1830171Reviewed-by: Alex Sakhartchouk <alexst@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701114}