Introduce NavigateToExistingPendingEntry in NavigationController

Following the introduction of NavigateWithoutEntry in
https://chromium-review.googlesource.com/c/chromium/src/+/904988, this
CL introduces a new function in NavigationController,
NavigateToExistingPendingEntry. This function should be used when requesting a
navigation to an existing NavigationEntry.

Bug: 803365, 803859
Change-Id: I2b1901c0e63934aac4df9837104dcb3f8f28fdc0
Reviewed-on: https://chromium-review.googlesource.com/1089052
Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Camille Lamy <clamy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573693}
2 files changed