bindings: Revert delete of frame check

In crrev.com/651588, I deleted a line to check if the frame is not
provisional by mistake.
https://chromium-review.googlesource.com/c/chromium/src/+/1256403/6/third_party/blink/renderer/bindings/core/v8/local_window_proxy.cc#b157

This CL reverts the change on the line.


Bug: 891130
Change-Id: I4db29876298a1b932f3bf0df07fb81a93681ee07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583030
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653921}
1 file changed