[ios] Implement FullscreenBrowserAgentObserving for toolbars
This CL implements the FullscreenBrowserAgentObserving protocol for
the primary and secondary toolbars as part of the ongoing fullscreen
refactoring. This allows the toolbars to provide their obscured inset
ranges and current states directly to the FullscreenBrowserAgent.
Specifically, BrowserViewController and the toolbar view controllers
now participate in the new state update flow, calculating and
providing their respective top and bottom obscured insets based on
the current fullscreen progress and toolbar configurations.
Fixed: 491864051, 491867342
Change-Id: I50f8688c0dac4d71bed0e63c8f180855348b8fe3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7717299
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Scott Yoder <scottyoder@google.com>
Reviewed-by: Aliona Dangla <alionadangla@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1609756}