Enable RenderTextHarfBuzz by default

ui/gfx/render_text_harfbuzz.cc

 // Copyright 2014 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/gfx/render_text_harfbuzz.h"
 
 #include <map>
 
 #include "base/debug/leak_annotations.h"
 #include "base/i18n/bidi_line_iterator.h"
@@ skipping 633 matching lines @@
     run = runs_[visual_to_logical_[visual_index]];
   }
   bool forward_motion = run->is_rtl == (direction == CURSOR_LEFT);
   return forward_motion ? FirstSelectionModelInsideRun(run) :
                           LastSelectionModelInsideRun(run);
 }
 
 SelectionModel RenderTextHarfBuzz::AdjacentWordSelectionModel(
     const SelectionModel& selection,
     VisualCursorDirection direction) {
-  // TODO(ckocagil): This implementation currently matches RenderTextWin, but it
-  // should match the native behavior on other platforms.
   if (obscured())
     return EdgeSelectionModel(direction);
 
   base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
   bool success = iter.Init();
   DCHECK(success);
   if (!success)
     return selection;
 
+  // Match OS specific word break behavior.
+#if defined(OS_WIN)
   size_t pos;
   if (direction == CURSOR_RIGHT) {
     pos = std::min(selection.caret_pos() + 1, text().length());
     while (iter.Advance()) {
       pos = iter.pos();
       if (iter.IsWord() && pos > selection.caret_pos())
         break;
     }
   } else {  // direction == CURSOR_LEFT
     // Notes: We always iterate words from the beginning.
@@ skipping 12 matching lines @@
           // The cursor is in the middle or at the end of a word.
           // Move to the top of current word.
           pos = begin;
           break;
         }
         pos = iter.pos() - iter.GetString().length();
       }
     }
   }
   return SelectionModel(pos, CURSOR_FORWARD);
+#else
+  SelectionModel cur(selection);
+  for (;;) {
+    cur = AdjacentCharSelectionModel(cur, direction);
+    size_t run = GetRunContainingCaret(cur);
+    if (run == runs_.size())
+      break;
+    const bool is_forward = runs_[run]->is_rtl == (direction == CURSOR_LEFT);
+    size_t cursor = cur.caret_pos();
+    if (is_forward ? iter.IsEndOfWord(cursor) : iter.IsStartOfWord(cursor))
+      break;
+  }
+  return cur;
+#endif
 }
 
 std::vector<Rect> RenderTextHarfBuzz::GetSubstringBounds(const Range& range) {
   DCHECK(!needs_layout_);
   DCHECK(Range(0, text().length()).Contains(range));
   Range layout_range(TextIndexToLayoutIndex(range.start()),
                      TextIndexToLayoutIndex(range.end()));
   DCHECK(Range(0, GetLayoutText().length()).Contains(layout_range));
 
   std::vector<Rect> rects;
@@ skipping 414 matching lines @@
     run->width +=
         SkScalarRoundToInt(SkFixedToScalar(hb_positions[i].x_advance));
   }
 
   hb_buffer_destroy(buffer);
   hb_font_destroy(harfbuzz_font);
   return true;
 }
 
 }  // namespace gfx