Add paint() function as valid CSS <image> type.

third_party/WebKit/Source/core/css/CSSPaintValue.cpp

+// Copyright 2016 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.
+
+#include "core/css/CSSPaintValue.h"
+
+#include "core/css/CSSCustomIdentValue.h"
+#include "platform/graphics/Image.h"
+#include "wtf/text/StringBuilder.h"
+
+namespace blink {
+
+CSSPaintValue::CSSPaintValue(PassRefPtrWillBeRawPtr<CSSCustomIdentValue> name)
+    : CSSImageGeneratorValue(PaintClass)
+    , m_name(name)
+{
+}
+
+CSSPaintValue::~CSSPaintValue()
+{
+}
+
+String CSSPaintValue::customCSSText() const
+{
+    StringBuilder result;
+    result.appendLiteral("paint(");
+    result.append(name());

[Timothy Loh, 2016/03/14 00:45:52]

Actually this probably needs to be m_name->customCSSText() since custom idents
can be written with escapes in custom idents, e.g. paint(\ ) would be serialized
as paint( ) with the current code.

[ikilpatrick, 2016/03/14 17:41:46]

Done.

+    result.append(')');
+    return result.toString();
+}
+
+String CSSPaintValue::name() const
+{
+    return m_name->value();
+}
+
+PassRefPtr<Image> CSSPaintValue::image(const LayoutObject*, const IntSize&)
+{
+    // TODO(ikilpatrick): implement.
+    return nullptr;
+}
+
+bool CSSPaintValue::equals(const CSSPaintValue& other) const
+{
+    return name() == other.name();
+}
+
+DEFINE_TRACE_AFTER_DISPATCH(CSSPaintValue)
+{
+    visitor->trace(m_name);
+    CSSImageGeneratorValue::traceAfterDispatch(visitor);
+}
+
+} // namespace blink