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

ui/gfx/text_utils.h

Index: ui/gfx/text_utils.h
diff --git a/ui/gfx/text_utils.h b/ui/gfx/text_utils.h
index 088f97cea9e6077ce461f40c3cfcad97a51d3ed1..46fef9a8e8fced61029104bcf76fa50979afdcb5 100644
--- a/ui/gfx/text_utils.h
+++ b/ui/gfx/text_utils.h
@@ -31,6 +31,16 @@ GFX_EXPORT int GetStringWidth(const base::string16& text,
 GFX_EXPORT float GetStringWidthF(const base::string16& text,
                                  const FontList& font_list);
 
+// Returns a valid cut boundary at or before |index|. The surrogate pair and
+// combined characters should not be separated.
+GFX_EXPORT size_t
+FindValidBoundaryBefore(const base::string16& text, size_t index);

[msw, 2015/06/03 00:32:04]

nit: Is this the correct line breaking according to the style guide? I thought
we only put the export and return type on a separate line if they didn't fit on
the same line as the function name without args. I suspect this should be
something like this (and ditto below):
GFX_EXPORT size_t FindValidBoundaryBefore(const base::string16& text,
                                          size_t index);

[xdai1, 2015/06/06 00:05:19]

Yes, this is the correct line breaking. It's generated by running "git cl
format". I agree it's weird...

+
+// Returns a valid cut boundary at or after |index|. The surrogate pair and
+// combined characters should not be separated.
+GFX_EXPORT size_t
+FindValidBoundaryAfter(const base::string16& text, size_t index);
+
 }  // namespace gfx
 
 #endif  // UI_GFX_TEXT_UTILS_H_