Re-land RenderTextHarfBuzz: Decide run direction by BiDi embedding level

ui/gfx/render_text_harfbuzz.h

Index: ui/gfx/render_text_harfbuzz.h
diff --git a/ui/gfx/render_text_harfbuzz.h b/ui/gfx/render_text_harfbuzz.h
index 4e27af9d882cc173f2ddf0700cbfd2a3b7deab36..db59a024cffb289fe0fad60fc9775b876cda0ce1 100644
--- a/ui/gfx/render_text_harfbuzz.h
+++ b/ui/gfx/render_text_harfbuzz.h
@@ -61,7 +61,7 @@ struct GFX_EXPORT TextRunHarfBuzz {
 
 }  // namespace internal
 
-class RenderTextHarfBuzz : public RenderText {
+class GFX_EXPORT RenderTextHarfBuzz : public RenderText {
  public:
   RenderTextHarfBuzz();
   virtual ~RenderTextHarfBuzz();
@@ -90,6 +90,9 @@ class RenderTextHarfBuzz : public RenderText {
   virtual void DrawVisualText(Canvas* canvas) OVERRIDE;
 
  private:
+  friend class RenderTextTest;
+  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_RunDirection);
+
   // Return the run index that contains the argument; or the length of the
   // |runs_| vector if argument exceeds the text length or width.
   size_t GetRunContainingCaret(const SelectionModel& caret) const;