Implemented the CSSPropertyAPI for the line-height property.

third_party/WebKit/Source/core/css/properties/CSSPropertyAPILineHeight.cpp

Index: third_party/WebKit/Source/core/css/properties/CSSPropertyAPILineHeight.cpp
diff --git a/third_party/WebKit/Source/core/css/properties/CSSPropertyAPILineHeight.cpp b/third_party/WebKit/Source/core/css/properties/CSSPropertyAPILineHeight.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..2be0560f248f72f6cf2c010fd27ce0566c371d76
--- /dev/null
+++ b/third_party/WebKit/Source/core/css/properties/CSSPropertyAPILineHeight.cpp
@@ -0,0 +1,18 @@
+// Copyright 2017 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/properties/CSSPropertyAPILineHeight.h"
+
+#include "core/css/parser/CSSParserContext.h"
+#include "core/css/properties/CSSPropertyFontUtils.h"
+
+namespace blink {
+
+const CSSValue* CSSPropertyAPILineHeight::parseSingleValue(
+    CSSParserTokenRange& range,
+    const CSSParserContext* context) {
+  return CSSPropertyFontUtils::consumeLineHeight(range, context->mode());
+}
+
+}  // namespace blink