Enable WebViewTest.NestedGuestContainerBounds for --site-per-process

The current implementation of BrowserPluginGuest::GetCoordinatesInEmbedderWebContents transforms
guest_view_rect_.origin() to root view coordinates, which is incorrect when the guest is inside
another guest. This is specifically true when PDF is embedded inside a <webview>.

This CL will add the logic to properly modify GetCoordinatsInEmbedderWebContents such that
the returned value is correctly within the coordinate of embedder.

BUG=581898
TBR=wjmaclean@chromium.org

Review-Url: https://codereview.chromium.org/2886013002
Cr-Commit-Position: refs/heads/master@{#472512}
2 files changed