Handle missing glyphs when adjusting spacing in SimpleShaper

Source/platform/fonts/shaping/SimpleShaper.cpp

Index: Source/platform/fonts/shaping/SimpleShaper.cpp
diff --git a/Source/platform/fonts/shaping/SimpleShaper.cpp b/Source/platform/fonts/shaping/SimpleShaper.cpp
index 24be19b9ee933caae0e3af3b62499483fc314198..cf8210b14818774a654e5fe7eb9ac263bc2f9dbe 100644
--- a/Source/platform/fonts/shaping/SimpleShaper.cpp
+++ b/Source/platform/fonts/shaping/SimpleShaper.cpp
@@ -207,7 +207,7 @@ unsigned SimpleShaper::advanceInternal(TextIterator& textIterator, GlyphBuffer*
             cacheFallbackFont(fontData, primaryFont);
         }
 
-        if (hasExtraSpacing)
+        if (hasExtraSpacing && width)

[pdr., 2014/10/13 23:53:30]

(Maybe as a followup) Can you add a bool to better describe what's going on when
width=0? This seems to have been first added back in
https://chromium.googlesource.com/chromium/blink/+/4a2a3ba905642998075cf4b161...
and it'll be easy to make this mistake again.

             width = adjustSpacing(width, charData, *fontData, glyphBuffer);

[pdr., 2014/10/13 23:53:30]

Does it make sense to check for width in adjustSpacing after this patch? I don't
fully understand the comment in adjustSpacing in the context of this patch.

 
         if (m_bounds)