Reland "Remove GTK scale factor workarounds"

This is a reland of 2c2f5494

Original change's description:
> Remove GTK scale factor workarounds
>
> The workarounds were initially added to fix rendering issues
> when the scale factor was an odd value like 1.01.  Hopefully
> the fractional scale factor support in Chrome is now good
> enough to handle these cases.
>
> This change prevents unexpected scale factor behavior like
> 1.25 remapping to 1.0.
>
> BUG=1033552
> R=oshima
>
> Change-Id: I1d22c1ddcf463fed12061ef265d2a6b4a4bcbeb8
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121179
> Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#753653}

CQ_INCLUDE_TRYBOTS=luci.chromium.try:linux-trusty-rel

Bug: 1033552
Change-Id: Ia0ce07eb61efa56a7c0d3e3ade4a167d73510f94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124889
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754224}

chrome/browser/ui/gtk/gtk_ui.cc

@@ -1093,15 +1093,19 @@ float GtkUi::GetRawDeviceScaleFactor() {
     return display::Display::GetForcedDeviceScaleFactor();
 
   GdkScreen* screen = gdk_screen_get_default();
-  gint scale = gtk_widget_get_scale_factor(fake_window_);
-  DCHECK_GT(scale, 0);
-  gdouble resolution = gdk_screen_get_resolution(screen);
-  const float scale_factor =
-      resolution <= 0 ? scale : resolution * scale / kDefaultDPI;
+  float scale = gtk_widget_get_scale_factor(fake_window_);
+  DCHECK_GT(scale, 0.0);
 
-  // Blacklist scaling factors <120% (crbug.com/484400) and round
-  // to 1 decimal to prevent rendering problems (crbug.com/485183).
-  return scale_factor < 1.2f ? 1.0f : roundf(scale_factor * 10) / 10;
+  gdouble resolution = gdk_screen_get_resolution(screen);
+  // TODO(https://crbug.com/1033552): Remove this hack once the Trusty bots are
+  // fixed to have a resolution of 96, or when the Trusty bots are removed
+  // altogether.
+  if (std::abs(resolution - 95.8486) < 0.001)
+    resolution = 96;
+  if (resolution > 0)
+    scale *= resolution / kDefaultDPI;
+
+  return scale;
 }
 
 void GtkUi::UpdateDeviceScaleFactor() {