Move user activation check to RemoteFrame::Navigate's callers.

Currently RemoteFrame::Navigate is the user of
Frame::HasTransientUserActivation that passes a RemoteFrame*, and
it seems wrong because the user activation (user gesture) needed by
the navigation should belong to the LocalFrame that initiated the
navigation.

Follow-up CLs after this one will update UserActivation code in
Frame to take a LocalFrame* instead of a Frame*, and get rid of
redundant IPCs.

Bug: 811414
Change-Id: I771c1694043edb54374a44213d16715d9c7da704
Reviewed-on: https://chromium-review.googlesource.com/914736
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536728}
bool HTMLFormElement::HasLegalLinkAttribute(const QualifiedName& name) const {
  return name == actionAttr || HTMLElement::HasLegalLinkAttribute(name);
}

bool HTMLFormElement::HasLegalLinkAttribute(const QualifiedName& name) const {
  return name == actionAttr || HTMLElement::HasLegalLinkAttribute(name);
}
