x11: Fix regression in _NET_WM_STATE_FULLSCREEN changes handling

crrev.com/c/1769450 removed X11-specific DWTHX11::{Set,Is}Fullscreen()
overrides in favor of DWTHPlatform versions, making chrome to enter/exit
browser fullscreen mode both when it is requested explicitly by the user (e.g:
Using F11 keybinding) as well as when it was requested by the other process,
e.g: custom WM keybinding to toggle _NET_WM_STATE_FULLSCREEN window state.
Such functionality change can be considered a regression as it violate EWMH
guidelines, which states:

> When a window-manager tells a window to become 'fullscreen', it is not
> telling the window to make a sub-selection of its contents fullscreen, but
> instead optimize the whole application for fullscreen usage. Window
> decorations (e.g. borders) should be hidden, but the functionalily of the
> application should not change.

This CL restores the previous behavior and test expectations. Additionally this
fixes an issue in window bounds tracking while it is in browser fullscreen mode
(but the X11 window is not in fullscreen state). Such issue was already present
before this regression has been introduced.

Bug: 1035772
Change-Id: Ief8fba7df2c5d2466da038c2b9edf1d928261c8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1989049
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Nick Yamane <nickdiego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#731721}
2 files changed