fix know issues in RenderText

ui/gfx/render_text_linux.cc

Index: ui/gfx/render_text_linux.cc
===================================================================
--- ui/gfx/render_text_linux.cc	(revision 100008)
+++ ui/gfx/render_text_linux.cc	(working copy)
@@ -123,13 +123,19 @@
 }
 
 SelectionModel RenderTextLinux::FindCursorPosition(const Point& point) {
-  // TODO(xji): when points outside of text, return HOME/END position.
   PangoLayout* layout = EnsureLayout();
 
   if (text().empty())
     return SelectionModel(0, 0, SelectionModel::LEADING);
 
   Point p(ToTextPoint(point));
+
+  // When the point is outside of text, return HOME/END position.
+  if (p.x() < 0)
+    return LeftEndSelectionModel();
+  else if (p.x() > GetStringWidth())
+    return RightEndSelectionModel();
+
   int caret_pos, trailing;
   pango_layout_xy_to_index(layout, p.x() * PANGO_SCALE, p.y() * PANGO_SCALE,
                            &caret_pos, &trailing);
@@ -175,6 +181,12 @@
   return bounds;
 }
 
+size_t RenderTextLinux::GetIndexOfNextGrapheme(size_t position) {
+  EnsureLayout();
+  size_t index = Utf16IndexToUtf8Index(position);
+  return Utf16IndexOfAdjacentGrapheme(index, NEXT);
+}
+
 SelectionModel RenderTextLinux::GetLeftSelectionModel(
     const SelectionModel& current,
     BreakType break_type) {
@@ -244,10 +256,13 @@
   return Utf16IndexOfAdjacentGrapheme(index, PREVIOUS);
 }
 
-size_t RenderTextLinux::GetIndexOfNextGrapheme(size_t position) {
+bool RenderTextLinux::IsCursorablePosition(size_t position) {
+  if (position == 0 && text().empty())
+    return true;
+
   EnsureLayout();
-  size_t index = Utf16IndexToUtf8Index(position);
-  return Utf16IndexOfAdjacentGrapheme(index, NEXT);
+  return (position >= 0 && position < static_cast<size_t>(num_log_attrs_) &&
+          log_attrs_[position].is_cursor_position);
 }
 
 GSList* RenderTextLinux::GetRunContainingPosition(size_t position) const {