[Squad] Clone ComputedStyle adjusting autosizing in test.

Getting rid of yet another mutable style access.

Bug: 813068
Change-Id: I227ccf577d0c0c90bc871c5eee3b768a6f140656
Reviewed-on: https://chromium-review.googlesource.com/1000732
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550564}

third_party/blink/renderer/core/exported/web_frame_test.cc

@@ -1267,9 +1267,11 @@ bool SetTextAutosizingMultiplier(Document* document, float multiplier) {
   for (LayoutObject* layout_object = document->GetLayoutView(); layout_object;
        layout_object = layout_object->NextInPreOrder()) {
     if (layout_object->Style()) {
-      layout_object->MutableStyleRef().SetTextAutosizingMultiplier(multiplier);
-
-      EXPECT_EQ(multiplier, layout_object->Style()->TextAutosizingMultiplier());
+      scoped_refptr<ComputedStyle> modified_style =
+          ComputedStyle::Clone(layout_object->StyleRef());
+      modified_style->SetTextAutosizingMultiplier(multiplier);
+      EXPECT_EQ(multiplier, modified_style->TextAutosizingMultiplier());
+      layout_object->SetStyleInternal(std::move(modified_style));
       multiplier_set = true;
     }
   }