Force software layer to redraw when it is resized.

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 2329cfb33551c1a378fd370597d0741c2c630b9b..6834df1304fd78d550c95a983fd8c2f584b6b3c4 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -2277,7 +2277,12 @@ void RenderWidgetHostViewMac::LayoutLayers() {
   // in the layer being anchored to the top-left. Set the layer's frame
   // explicitly, since this is more reliable in practice.
   if (software_layer_) {
-    [software_layer_ setFrame:new_background_frame];
+    bool frame_changed = !CGRectEqualToRect(
+        new_background_frame, [software_layer_ frame]);
+    if (frame_changed) {
+      [software_layer_ setFrame:new_background_frame];
+      [software_layer_ setNeedsDisplay];
+    }
   }
 }