[Squad] Modify LayoutObject direction in cloned style.

Gets rid of MutableStyleRef() in test.

Bug: 813068
Change-Id: I3ee3d2e13223164c2b3ca32c69989f3f573e0cf4
Reviewed-on: https://chromium-review.googlesource.com/984877
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546698}

third_party/WebKit/Source/core/html/forms/HTMLFormControlElementTest.cpp

@@ -91,7 +91,10 @@ TEST_F(HTMLFormControlElementTest, customValidationMessageTextDirection) {
   EXPECT_EQ(TextDirection::kRtl, message_dir);
   EXPECT_EQ(TextDirection::kLtr, sub_message_dir);
 
-  input->GetLayoutObject()->MutableStyleRef().SetDirection(TextDirection::kRtl);
+  scoped_refptr<ComputedStyle> rtl_style =
+      ComputedStyle::Clone(input->GetLayoutObject()->StyleRef());
+  rtl_style->SetDirection(TextDirection::kRtl);
+  input->GetLayoutObject()->SetStyle(std::move(rtl_style));
   input->FindCustomValidationMessageTextDirection(message, message_dir,
                                                   sub_message, sub_message_dir);
   EXPECT_EQ(TextDirection::kRtl, message_dir);