commit 2ae993fad864e5c683d009ebdfbb0bdae3faef44
author lukasza <lukasza@chromium.org> Tue Sep 13 20:28:10 2016
committer Commit bot <commit-bot@chromium.org> Tue Sep 13 20:30:28 2016
tree 26b656b840c1642538de64eae523c9439aedbc55
parent 7532c960faf5f59ef7031e4488fce36b6e1c1cf0

Avoid mutating frame unique name after first real commit.

History navigations depend on frame unique names to identify frames that
need to load their state from history.  This identification is broken if
a frame's unique name can change throughout frame's lifetime.  For
example - the newly added layout tests fails (before FrameTree.cpp
changes introduced by this CL) to correctly navigate the subframe after
a back navigation.

BUG=607205

Review-Url: https://codereview.chromium.org/2317203002
Cr-Commit-Position: refs/heads/master@{#418350}