Implement Pango RenderText for Linux.

ui/gfx/render_text.cc

Index: ui/gfx/render_text.cc
===================================================================
--- ui/gfx/render_text.cc	(revision 97029)
+++ ui/gfx/render_text.cc	(working copy)
@@ -199,8 +199,7 @@
   // Cancelling a selection moves to the edge of the selection.
   if (break_type != LINE_BREAK && !EmptySelection() && !select) {
     // Use the selection start if it is left of the selection end.
-    SelectionModel selection_start(GetSelectionStart(), GetSelectionStart(),
-                                   SelectionModel::LEADING);
+    SelectionModel selection_start =  GetSelectionModelForSelectionStart();
     if (GetCursorBounds(selection_start, false).x() <
         GetCursorBounds(position, false).x())
       position = selection_start;
@@ -221,8 +220,7 @@
   // Cancelling a selection moves to the edge of the selection.
   if (break_type != LINE_BREAK && !EmptySelection() && !select) {
     // Use the selection start if it is right of the selection end.
-    SelectionModel selection_start(GetSelectionStart(), GetSelectionStart(),
-                                   SelectionModel::LEADING);
+    SelectionModel selection_start = GetSelectionModelForSelectionStart();
     if (GetCursorBounds(selection_start, false).x() >
         GetCursorBounds(position, false).x())
       position = selection_start;
@@ -608,4 +606,16 @@
   cursor_bounds_.Offset(delta_offset, 0);
 }
 
+SelectionModel RenderText::GetSelectionModelForSelectionStart() {
+  if (GetSelectionStart() < GetCursorPosition()) {
+    return SelectionModel(GetSelectionStart(),
+                          GetSelectionStart(),
+                          SelectionModel::LEADING);
+  } else {
+    return SelectionModel(GetSelectionStart(),
+                          GetIndexOfPreviousGrapheme(GetSelectionStart()),
+                          SelectionModel::TRAILING);
+  }
+}
+
 }  // namespace gfx