Fix AutoResize mode on Retina displays

The compositor viewport wasn't getting set correctly for platforms that
didn't use DSF and had a scale factor on the display. Ensure it is
correct.

This was caused by
https://chromium-review.googlesource.com/c/chromium/src/+/2402116
incorrectly using size_ assuming it was the same for the viewport pixel
rect, but that is not the case for platforms without Zoom for DSF
(such as Mac).

BUG=1131162

Change-Id: Ie07ad887cf8dd511689a91011c928997c3587b2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2425195Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809693}

third_party/blink/renderer/core/frame/web_view_frame_widget.cc

@@ -524,7 +524,9 @@ void WebViewFrameWidget::ApplyVisualPropertiesSizing(
   gfx::Rect new_compositor_viewport_pixel_rect =
       visual_properties.compositor_viewport_pixel_rect;
   if (AutoResizeMode()) {
-    new_compositor_viewport_pixel_rect = gfx::Rect(size_);
+    new_compositor_viewport_pixel_rect = gfx::Rect(gfx::ScaleToCeiledSize(
+        widget_base_->BlinkSpaceToDIPs(size_),
+        visual_properties.screen_info.device_scale_factor));
   }
 
   widget_base_->UpdateSurfaceAndScreenInfo(