http://crbug.com/223500
http://trac.webkit.org/changeset/143337/trunk/Source/WebCore/platform/graphics/harfbuzz/HarfBuzzShaper.cpp

Index: trunk/Source/WebCore/platform/graphics/harfbuzz/HarfBuzzShaper.cpp
===================================================================
--- trunk/Source/WebCore/platform/graphics/harfbuzz/HarfBuzzShaper.cpp	(revision 142928)
+++ trunk/Source/WebCore/platform/graphics/harfbuzz/HarfBuzzShaper.cpp	(revision 143337)
@@ -330,4 +330,7 @@
         if (shouldSetDirection)
             hb_buffer_set_direction(harfBuzzBuffer.get(), currentRun->rtl() ? HB_DIRECTION_RTL : HB_DIRECTION_LTR);
+        else
+            // Leaving direction to HarfBuzz to guess is *really* bad, but will do for now.
+            hb_buffer_guess_segment_properties(harfBuzzBuffer.get());
 
         // Add a space as pre-context to the buffer. This prevents showing dotted-circle