Move the last committed URL from FrameTreeNode to RenderFrameHostImpl.

This avoids bugs where callers of RenderFrameHost::GetLastCommittedURL
get the wrong value because they called it on the pending RFH.

BUG=590034
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Review URL: https://codereview.chromium.org/1717023002

Cr-Commit-Position: refs/heads/master@{#377756}
6 files changed