[ChromeDriver] Make ExecuteSwitchToFrame() W3C compliant

Bug: chromedriver:1992
Change-Id: If7729d68d753459a9b27fc52d053d5f065341c24
Reviewed-on: https://chromium-review.googlesource.com/1229188
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Tatiana Buldina <buldina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591868}
4 files changed