Stop combining text runs which are connected by 'COMMON' blocks.

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 6d8fa8d962a13e7067e0d2f759cf8f9dbdb89916..e24770c9c3e86306e3aa2a2c1c829acfa4f894fa 100644
--- a/ui/gfx/render_text_harfbuzz.h
+++ b/ui/gfx/render_text_harfbuzz.h
@@ -115,6 +115,10 @@ class TextRunList {
   // Do not use this when multiline is enabled.
   float width() const { return width_; }
 
+  // Get the run applicable to |position| (at or preceeding |position|).
+  typedef ScopedVector<TextRunHarfBuzz>::const_iterator TextRunHarfBuzzIter;
+  TextRunHarfBuzzIter GetRunAt(size_t position) const;
+
  private:
   // Text runs in logical order.
   ScopedVector<TextRunHarfBuzz> runs_;
@@ -168,6 +172,7 @@ class GFX_EXPORT RenderTextHarfBuzz : public RenderText {
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, Multiline_HorizontalAlignment);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, Multiline_NormalWidth);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, Multiline_WordWrapBehavior);
+  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, Multiline_LineBreakerBehavior);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_RunDirection);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_HorizontalPositions);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest,