Fix TextIterator's behavior with first-letter

third_party/WebKit/Source/core/editing/iterators/TextIteratorTextState.cpp

Index: third_party/WebKit/Source/core/editing/iterators/TextIteratorTextState.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/TextIteratorTextState.cpp b/third_party/WebKit/Source/core/editing/iterators/TextIteratorTextState.cpp
index 5e45a354e2b5a33de171bf796289b2a97aa7bf2d..06262fb3c1c295ddda943d6406850f37a6f6d2fe 100644
--- a/third_party/WebKit/Source/core/editing/iterators/TextIteratorTextState.cpp
+++ b/third_party/WebKit/Source/core/editing/iterators/TextIteratorTextState.cpp
@@ -39,7 +39,8 @@ TextIteratorTextState::TextIteratorTextState(bool emitsOriginalText)
       m_positionEndOffset(0),
       m_hasEmitted(false),
       m_lastCharacter(0),
-      m_emitsOriginalText(emitsOriginalText) {}
+      m_emitsOriginalText(emitsOriginalText),
+      m_textStartOffset(0) {}
 
 UChar TextIteratorTextState::characterAt(unsigned index) const {
   SECURITY_DCHECK(index < static_cast<unsigned>(length()));
@@ -95,12 +96,14 @@ void TextIteratorTextState::updateForReplacedElement(Node* baseNode) {
 
   m_textLength = 0;
   m_lastCharacter = 0;
+  m_textStartOffset = 0;
 }
 
 void TextIteratorTextState::emitAltText(Node* node) {
   m_text = toHTMLElement(node)->altText();
   m_textLength = m_text.length();
   m_lastCharacter = m_textLength ? m_text[m_textLength - 1] : 0;
+  m_textStartOffset = 0;
 }
 
 void TextIteratorTextState::flushPositionOffsets() const {
@@ -136,6 +139,7 @@ void TextIteratorTextState::spliceBuffer(UChar c,
 
   // remember some iteration state
   m_lastCharacter = c;
+  m_textStartOffset = 0;
 }
 
 void TextIteratorTextState::emitText(Node* textNode,
@@ -161,6 +165,7 @@ void TextIteratorTextState::emitText(Node* textNode,
   m_lastCharacter = m_text[textEndOffset - 1];
 
   m_hasEmitted = true;
+  m_textStartOffset = layoutObject->textStartOffset();
 }
 
 void TextIteratorTextState::appendTextTo(ForwardsTextBuffer* output,