Handle kNavigationPolicyHandledByClientForInitialHistory separately

This patch verifies a number of assumptions and just marks the frame
as loading for the kNavigationPolicyHandledByClientForInitialHistory
case. The assumptions are:
- there is no provisional document loader;
- the existing (empty) document has finished parsing and completed loading.

This patch will make it possible to call CommitNavigation directly
for the case of kNavigationPolicyCurrentTab.

Bug: 855189
Change-Id: I9c36bbea2e65e370ad7483b39428735fd2739c0a
Reviewed-on: https://chromium-review.googlesource.com/1228891
Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591866}
1 file changed