mustash: Fix scale factor for bad physical_size.

On daisy devices the physical_size for display is being reported
incorrectly as (0, 0). Return a standard DPI in this case.

I've filled crbug.com/669554 for the bad physical_size value.

BUG=669554

Review-Url: https://codereview.chromium.org/2539843002
Cr-Commit-Position: refs/heads/master@{#435037}

services/ui/display/platform_screen_ozone.cc

@@ -28,7 +28,13 @@ const float kInchInMm = 25.4f;
 
 float ComputeDisplayDPI(const gfx::Size& pixel_size,
                         const gfx::Size& physical_size) {
-  DCHECK(!physical_size.IsEmpty());
+  // The physical_size is broken for some devices, return standard DPI. See
+  // crbug.com/669554.
+  if (physical_size.IsEmpty()) {
+    LOG(ERROR) << "Display has empty phsical_size";
+    return 96.0f;
+  }
+
   return (pixel_size.width() / static_cast<float>(physical_size.width())) *
          kInchInMm;
 }