Add full offset mapping construction in a block

third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.h

Index: third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.h
diff --git a/third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.h b/third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.h
new file mode 100644
index 0000000000000000000000000000000000000000..12b0becb896cb0e938da6964c3ee1964c694aa1a
--- /dev/null
+++ b/third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.h
@@ -0,0 +1,65 @@
+// 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.
+
+#ifndef NGOffsetMappingResult_h
+#define NGOffsetMappingResult_h
+
+#include "platform/wtf/Allocator.h"
+#include "platform/wtf/Vector.h"
+
+namespace blink {
+
+class LayoutText;
+
+enum class NGOffsetMappingUnitType { kIdentity, kCollapsed, kExpanded };
+
+// An NGOffsetMappingUnit indicates a "simple" offset mapping between dom offset
+// range [dom_start, dom_end] on node |owner| and text content offset range
+// [text_content_start, text_content_end]. The mapping between them falls in one
+// of the following categories, depending on |type|:
+// - kIdentity: The mapping between the two ranges is the identity mapping. In
+//   other words, the two ranges have the same length, and the offsets are
+//   mapped one-to-one.
+// - kCollapsed: The mapping is collapsed, namely, |text_content_start| and
+//   |text_content_end| are the same, and characters in the dom range are
+//   collapsed.
+// - kExpanded: The mapping is expanded, namely, |dom_end == dom_start + 1|, and
+//   |text_content_end > text_content_start + 1|, indicating that the character
+//   in the dom range is expanded into multiple characters.
+// See design doc https://goo.gl/CJbxky for details.
+struct NGOffsetMappingUnit {
+  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
+
+  NGOffsetMappingUnitType type = NGOffsetMappingUnitType::kIdentity;
+
+  // Ideally, we should store |Node| as owner, instead of |LayoutObject|.
+  // However, we need to ensure the invariant that, units of the same owner are
+  // consecutive in |NGOffsetMappingResult::units|. This might have a subtle
+  // conflict with :first-letter if, during inline collection, there there are
+  // other strings collected between the first letter and the remaining text of
+  // the node.
+  // TODO(xiaochengh): Figure out if this the issue really exists. If not, then
+  // we should use |Node| as owner.
+  const LayoutText* owner = nullptr;
+
+  unsigned dom_start = 0;
+  unsigned dom_end = 0;
+  unsigned text_content_start = 0;
+  unsigned text_content_end = 0;
+};
+
+// An NGOffsetMappingResult stores the units of a LayoutNGBlockFlow in sorted
+// order in a vector. For each text node, the index range of the units owned by
+// the node is also stored.
+// See design doc https://goo.gl/CJbxky for details.
+struct NGOffsetMappingResult {
+  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
+
+  Vector<NGOffsetMappingUnit> units;
+  HashMap<const LayoutText*, std::pair<unsigned, unsigned>> ranges;
+};
+
+}  // namespace blink
+
+#endif  // NGOffsetMappingResult_h