Ignore Unicode BiDi control characters in missing glyphs check in RenderTextWin.

ui/gfx/render_text_win.cc

Index: ui/gfx/render_text_win.cc
===================================================================
--- ui/gfx/render_text_win.cc	(revision 144927)
+++ ui/gfx/render_text_win.cc	(working copy)
@@ -224,6 +224,17 @@
     *font = font->DeriveFont(font_size - current_size, font_style);
 }
 
+// Returns true if |c| is a Unicode BiDi control character.
+bool IsUnicodeBidiControlCharacter(char16 c) {
+  return c == base::i18n::kRightToLeftMark ||
+         c == base::i18n::kLeftToRightMark ||
+         c == base::i18n::kLeftToRightEmbeddingMark ||
+         c == base::i18n::kRightToLeftEmbeddingMark ||
+         c == base::i18n::kPopDirectionalFormatting ||
+         c == base::i18n::kLeftToRightOverride ||
+         c == base::i18n::kRightToLeftOverride;
+}
+
 }  // namespace
 
 namespace internal {
@@ -844,7 +855,8 @@
     // See: http://crbug.com/125629
     if (run->glyphs[glyph_index] == properties.wgBlank &&
         run->visible_attributes[glyph_index].fZeroWidth &&
-        !IsWhitespace(run_text[char_index])) {
+        !IsWhitespace(run_text[char_index]) &&
+        !IsUnicodeBidiControlCharacter(run_text[char_index])) {

[xji, 2012/06/29 23:13:19]

so, it always return wgBlank && fZeroWidth for bidi-ctrl characters?  which is a
false positive.

but how about there indeed were no glyph for those bidi-ctrl characters? (guess
win7 has them by default).

[Alexei Svitkine (slow), 2012/06/29 23:26:03]

We don't care about the cases where it doesn't return a wgBlank / not zero width
since it won't hit the false positive case.

If there are no glyphs returned for those, then it's fine as well.

       return true;
     }
   }