[Merge to M63] Gtk3: Fix frame button scaling on HIDPI

> This CL fixes frame buttons being too small when GDK_SCALE=2, as seen
> in [1].
>
> [1] https://bugs.chromium.org/p/chromium/issues/detail?id=753067#c43
>
> BUG=753067
> R=erg@chromium.org
>
> Change-Id: I835668b779ab10ab3da971960794093f37813141
> Reviewed-on: https://chromium-review.googlesource.com/729568
> Reviewed-by: Elliot Glaysher <erg@chromium.org>
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#510498}

BUG=753067
TBR=erg@chromium.org
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Change-Id: Ia68e0ebbb9f4456852098a42f7fd007d6ac96296
Reviewed-on: https://chromium-review.googlesource.com/736810
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/branch-heads/3239@{#199}
Cr-Branched-From: adb61db19020ed8ecee5e91b1a0ea4c924ae2988-refs/heads/master@{#508578}
1 file changed