Added CSSPropertyOffsetPathUtils which holds shared parsing logic.

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

Index: third_party/WebKit/Source/core/css/properties/CSSPropertyOffsetPathUtils.cpp
diff --git a/third_party/WebKit/Source/core/css/properties/CSSPropertyOffsetPathUtils.cpp b/third_party/WebKit/Source/core/css/properties/CSSPropertyOffsetPathUtils.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..7ab21f67aa9111ae46d1b125aa0359c6b3a32975
--- /dev/null
+++ b/third_party/WebKit/Source/core/css/properties/CSSPropertyOffsetPathUtils.cpp
@@ -0,0 +1,71 @@
+// 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/CSSPropertyOffsetPathUtils.h"
+
+#include "core/css/CSSPathValue.h"
+#include "core/css/parser/CSSParserContext.h"
+#include "core/css/parser/CSSPropertyParserHelpers.h"
+#include "core/svg/SVGPathByteStream.h"
+#include "core/svg/SVGPathUtilities.h"
+
+namespace blink {
+
+namespace {
+
+CSSValue* ConsumePath(CSSParserTokenRange& range) {
+  // FIXME: Add support for <url>, <basic-shape>, <geometry-box>.
+  if (range.Peek().FunctionId() != CSSValuePath)
+    return nullptr;
+
+  CSSParserTokenRange function_range = range;
+  CSSParserTokenRange function_args =
+      CSSPropertyParserHelpers::ConsumeFunction(function_range);
+
+  if (function_args.Peek().GetType() != kStringToken)
+    return nullptr;
+  String path_string =
+      function_args.ConsumeIncludingWhitespace().Value().ToString();
+
+  std::unique_ptr<SVGPathByteStream> byte_stream = SVGPathByteStream::Create();
+  if (BuildByteStreamFromString(path_string, *byte_stream) !=
+          SVGParseStatus::kNoError ||
+      !function_args.AtEnd())
+    return nullptr;

[Eric Willigers, 2017/04/13 21:18:12]

I'd wrap this line in { } as the condition is spread across multiple lines.

[Bugs Nash, 2017/04/17 23:17:36]

done

+
+  range = function_range;
+  if (byte_stream->IsEmpty())
+    return CSSIdentifierValue::Create(CSSValueNone);
+  return CSSPathValue::Create(std::move(byte_stream));
+}
+
+}  // namespace
+
+CSSValue* CSSPropertyOffsetPathUtils::ConsumeOffsetPath(
+    CSSParserTokenRange& range,
+    const CSSParserContext* context,
+    bool is_motion_path) {
+  CSSValue* value = ConsumePathOrNone(range);
+
+  // Count when we receive a valid path other than 'none'.
+  if (value && !value->IsIdentifierValue()) {
+    if (is_motion_path) {
+      context->Count(UseCounter::kCSSMotionInEffect);
+    } else {
+      context->Count(UseCounter::kCSSOffsetInEffect);
+    }
+  }
+  return value;
+}
+
+CSSValue* CSSPropertyOffsetPathUtils::ConsumePathOrNone(
+    CSSParserTokenRange& range) {
+  CSSValueID id = range.Peek().Id();
+  if (id == CSSValueNone)
+    return CSSPropertyParserHelpers::ConsumeIdent(range);
+
+  return ConsumePath(range);
+}
+
+}  // namespace blink