Allow resetting aspect ratio behavior on Linux

Electron has exposed methods to allow setting the aspect ratio
for a given window, and as a part of that needed to allow users to
reset the aspect ratio. On macOS, we could do that using
https://github.com/electron/electron/blob/3ae3233e65aa71b4815e156cd426834c30eb993b/shell/browser/native_window_mac.mm#L807-L816
, but on Linux this was not possible with currently exposed APIs without
this patch.

Change-Id: Ief3abea2322a734efe3e61b72df4d77daa88fb97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895789Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714850}

ui/base/x/x11_window.cc

@@ -742,9 +742,12 @@ void XWindow::SetXWindowAspectRatio(const gfx::SizeF& aspect_ratio) {
   long supplied_return;
 
   XGetWMNormalHints(xdisplay_, xwindow_, &size_hints, &supplied_return);
-  size_hints.flags |= PAspect;
-  size_hints.min_aspect.x = size_hints.max_aspect.x = aspect_ratio.width();
-  size_hints.min_aspect.y = size_hints.max_aspect.y = aspect_ratio.height();
+  // Unforce aspect ratio is parameter length is 0, otherwise set normally.
+  if (!aspect_ratio.IsEmpty()) {
+    size_hints.flags |= PAspect;
+    size_hints.min_aspect.x = size_hints.max_aspect.x = aspect_ratio.width();
+    size_hints.min_aspect.y = size_hints.max_aspect.y = aspect_ratio.height();
+  }
   XSetWMNormalHints(xdisplay_, xwindow_, &size_hints);
 }