Make InsertIncrementalTextCommand to handle surrogate pair

third_party/WebKit/Source/core/editing/commands/InsertIncrementalTextCommand.cpp

 // Copyright (c) 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/editing/commands/InsertIncrementalTextCommand.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/Text.h"
 #include "core/editing/EditingUtilities.h"
 #include "core/editing/Editor.h"
 #include "core/editing/PlainTextRange.h"
 #include "core/editing/VisibleUnits.h"
 #include "core/editing/iterators/CharacterIterator.h"
+#include "core/editing/state_machines/ForwardCodePointStateMachine.h"
 #include "core/html/HTMLSpanElement.h"
 
 namespace blink {
 
 namespace {
 
 size_t computeCommonPrefixLength(const String& str1, const String& str2) {
   const size_t maxCommonPrefixLength = std::min(str1.length(), str2.length());
+  ForwardCodePointStateMachine codePointStateMachine;
+  int result = 0;
   for (size_t index = 0; index < maxCommonPrefixLength; ++index) {
     if (str1[index] != str2[index])
-      return index;
+      return result;
+    codePointStateMachine.feedFollowingCodeUnit(str1[index]);
+    if (!codePointStateMachine.atCodePointBoundary())
+      continue;
+    result = index;
   }
   return maxCommonPrefixLength;
 }
 
 size_t computeCommonSuffixLength(const String& str1, const String& str2) {
   const size_t length1 = str1.length();
   const size_t length2 = str2.length();
   const size_t maxCommonSuffixLength = std::min(length1, length2);
   for (size_t index = 0; index < maxCommonSuffixLength; ++index) {
     if (str1[length1 - index - 1] != str2[length2 - index - 1])

[Changwan Ryu, 2017/03/29 15:36:57]

Could you consider doing the same for this function?

[yosin_UTC9, 2017/04/03 05:27:28]

I'll do in another patch.

       return index;
   }
   return maxCommonSuffixLength;
 }
 
 // If current position is at grapheme boundary, return 0; otherwise, return the
 // distance to its nearest left grapheme boundary.
 size_t computeDistanceToLeftGraphemeBoundary(const Position& position) {
   const Position& adjustedPosition = previousPositionOf(
       nextPositionOf(position, PositionMoveType::GraphemeCluster),
@@ skipping 130 matching lines @@
   const VisibleSelection& selectionForInsertion = computeSelectionForInsertion(
       selectionRange, offset, length, endingSelection().isDirectional());
 
   setEndingSelectionWithoutValidation(selectionForInsertion.start(),
                                       selectionForInsertion.end());
 
   InsertTextCommand::doApply(editingState);
 }
 
 }  // namespace blink