Use text affinity to return correct accessible line boundaries.

ui/accessibility/ax_text_utils.cc

 // Copyright (c) 2011 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 "ui/accessibility/ax_text_utils.h"
 
 #include "base/i18n/break_iterator.h"
 #include "base/logging.h"
 #include "base/strings/string_util.h"
 
 namespace ui {
 
 // line_breaks is a Misnomer. Blink provides the start offsets of each line
 // not the line breaks.
 // TODO(nektar): Rename line_breaks a11y attribute and variable references.
 size_t FindAccessibleTextBoundary(const base::string16& text,
                                   const std::vector<int>& line_breaks,
                                   TextBoundaryType boundary,
                                   size_t start_offset,
-                                  TextBoundaryDirection direction) {
+                                  TextBoundaryDirection direction,
+                                  AXTextAffinity affinity) {
   size_t text_size = text.size();
   DCHECK_LE(start_offset, text_size);
 
   if (boundary == CHAR_BOUNDARY) {
     if (direction == FORWARDS_DIRECTION && start_offset < text_size)
       return start_offset + 1;
     else
       return start_offset;
   }
 
   base::i18n::BreakIterator word_iter(text,
                                       base::i18n::BreakIterator::BREAK_WORD);
   if (boundary == WORD_BOUNDARY) {
     if (!word_iter.Init())
       return start_offset;
   }
 
   if (boundary == LINE_BOUNDARY) {
     if (direction == FORWARDS_DIRECTION) {
       for (size_t j = 0; j < line_breaks.size(); ++j) {
           size_t line_break = line_breaks[j] >= 0 ? line_breaks[j] : 0;
-        if (line_break > start_offset)
+        if ((affinity == AX_TEXT_AFFINITY_DOWNSTREAM &&
+             line_break > start_offset) ||
+            (affinity == AX_TEXT_AFFINITY_UPSTREAM &&
+             line_break >= start_offset)) {
           return line_break;
+        }
       }
       return text_size;
     } else {
       for (size_t j = line_breaks.size(); j != 0; --j) {
         size_t line_break = line_breaks[j - 1] >= 0 ? line_breaks[j - 1] : 0;
-        if (line_break <= start_offset)
+        if ((affinity == AX_TEXT_AFFINITY_DOWNSTREAM &&
+             line_break <= start_offset) ||
+            (affinity == AX_TEXT_AFFINITY_UPSTREAM &&
+             line_break < start_offset)) {
           return line_break;
+        }
       }
       return 0;
     }
   }
 
   size_t result = start_offset;
   for (;;) {
     size_t pos;
     if (direction == FORWARDS_DIRECTION) {
       if (result >= text_size)
@@ skipping 36 matching lines @@
 
     if (direction == FORWARDS_DIRECTION) {
       result++;
     } else {
       result--;
     }
   }
 }
 
 }  // namespace ui