Make NGInlineItemsBuilder construct whitespace-collapsed offset mapping

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

Index: third_party/WebKit/Source/core/layout/ng/inline/ng_inline_items_builder.h
diff --git a/third_party/WebKit/Source/core/layout/ng/inline/ng_inline_items_builder.h b/third_party/WebKit/Source/core/layout/ng/inline/ng_inline_items_builder.h
index 87195e47d6e86f89ed62efaba12d89120f17619d..f3c57682517770ecdc9a4a62ad6fa876befd29b7 100644
--- a/third_party/WebKit/Source/core/layout/ng/inline/ng_inline_items_builder.h
+++ b/third_party/WebKit/Source/core/layout/ng/inline/ng_inline_items_builder.h
@@ -17,6 +17,7 @@ namespace blink {
 class ComputedStyle;
 class LayoutObject;
 class NGInlineItem;
+class NGOffsetMappingBuilder;
 
 // NGInlineItemsBuilder builds a string and a list of NGInlineItem from inlines.
 //
@@ -27,11 +28,20 @@ class NGInlineItem;
 // By calling EnterInline/ExitInline, it inserts bidirectional control
 // characters as defined in:
 // https://drafts.csswg.org/css-writing-modes-3/#bidi-control-codes-injection-table
+//
+// NGInlineItemsBuilder may optionally take an NGOffsetMappingBuilder parameter
+// to construct the white-space collapsed offset mapping, which maps offsets in
+// the concatenation of all appended strings and characters to offsets in
+// |text_|. See https://goo.gl/CJbxky for more details about offset mapping.
 class CORE_EXPORT NGInlineItemsBuilder {
   STACK_ALLOCATED();
 
  public:
-  explicit NGInlineItemsBuilder(Vector<NGInlineItem>* items) : items_(items) {}
+  explicit NGInlineItemsBuilder(Vector<NGInlineItem>* items)
+      : items_(items), mapping_builder_(nullptr) {}
+  explicit NGInlineItemsBuilder(Vector<NGInlineItem>* items,
+                                NGOffsetMappingBuilder* mapping_builder)
+      : items_(items), mapping_builder_(mapping_builder) {}
   ~NGInlineItemsBuilder();
 
   String ToString();
@@ -98,6 +108,8 @@ class CORE_EXPORT NGInlineItemsBuilder {
   bool is_svgtext_ = false;
   bool has_bidi_controls_ = false;
 
+  NGOffsetMappingBuilder* mapping_builder_;
+
   void AppendWithWhiteSpaceCollapsing(const String&,
                                       unsigned start,
                                       unsigned end,