[devtools] Ignore layout requests to zero width/height

When a wayland user drags the Chrome window from maximized to a smaller
window size, we receive 2 layout requests: The first is always to zero
width and the second has the actual widht of the smaller window.

Since we do an actual layout with 0 width first and then persist that
width, the DevTools window actually vanishes as the second layout keeps
the DevTools size at 0.

Lets ignore a layout to 0 width for now. We are not sure if these
layout requests should be filtered out at a higher level, but this
fixes the bug until then.

R=pfaffe@chromium.org

Fixed: 434512352
Change-Id: Id9c9651da721c3a9f2db46e7f79df07aff015913
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7021118
Reviewed-by: Mike Wasserman <msw@chromium.org>
Reviewed-by: Philip Pfaffe <pfaffe@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1527966}