<webview>: Make contentWindow available prior to attachment (on display:none).
This CL updates the createGuest API to return an optional contentWindow.
This CL renames GuestSizer to GuestProxyHost which better represents what it does.
GuestProxyHost exposes "LoadURLWithParams" which, after navigating, creates a swapped out RenderView for the guest in the embedder's process.
This CL removes RegisterDestructionCallback from BrowserPluginGuestDelegate.
BUG=456118
Test=WebViewTest.NoContentSettingsAPI runs with display:none now.
Review URL: https://codereview.chromium.org/910073003
Cr-Commit-Position: refs/heads/master@{#319833}
20 files changed