Remove StyleEngine.h include from RenderObject.h

Source/core/rendering/RenderObjectStyle.h

Index: Source/core/rendering/RenderObjectStyle.h
diff --git a/Source/core/rendering/RenderObjectStyle.h b/Source/core/rendering/RenderObjectStyle.h
new file mode 100644
index 0000000000000000000000000000000000000000..ae8754569a1152cb927987d1b086904b4b80858c
--- /dev/null
+++ b/Source/core/rendering/RenderObjectStyle.h
@@ -0,0 +1,25 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef RenderObjectStyle_h
+#define RenderObjectStyle_h
+
+#include "core/dom/StyleEngine.h"
+#include "core/rendering/RenderObject.h"
+
+namespace WebCore {
+
+inline RenderStyle* RenderObject::firstLineStyle() const
+{
+    return document().styleEngine()->usesFirstLineRules() ? cachedFirstLineStyle() : style();

[esprehn, 2014/06/25 20:09:21]

I suspect neither of these really needs to be inline, can you just move them to
RenderObject.cpp instead?

[davve, 2014/06/26 07:00:33]

Sure.

But as is made more visible in https://codereview.chromium.org/355843002/
style(bool) (renamed to styleOrFirstLineStyle) is currently used in several
inlined functions:

InlineBox::verticalAlign()
InlineFlowBox::borderLogical{Left,Right}
requiresLineBoxForContent
BreakingContext::handleText

This made me hesitant to outline them, because I'm not sure how I would measure
the performance impact. But perhaps we can trust the performance bots on that
and do something like this in as a fall-back plan?

[davve, 2014/06/26 13:30:44]

I do seem get performance regressions when I try this locally.
Layout/line-layout.html seems to become around 3-4% slower.
Layout/line-layout-line-height.html is affected as well.

I tried to reproduce it on the bots on
https://codereview.chromium.org/359603002/ but have probably mistyped
the configuration or something. I can't read the output of the failure
for some reason.

+}
+
+inline RenderStyle* RenderObject::styleOrFirstLineStyle(bool firstLine) const
+{
+    return firstLine ? firstLineStyle() : style();
+}
+
+}
+
+#endif