bug 615121 - fix operator precedence error in glyph yoffset. r=jfkthame a=blocking-betaN

gfx/thebes/gfxFont.h

@@ -1793,7 +1793,7 @@ public:
         /** The advance, x-offset and y-offset of the glyph, in appunits
          *  mAdvance is in the text direction (RTL or LTR)
          *  mXOffset is always from left to right
-         *  mYOffset is always from bottom to top */   
+         *  mYOffset is always from top to bottom */   
         PRInt32  mAdvance;
         float    mXOffset, mYOffset;
     };

gfx/thebes/gfxHarfBuzzShaper.cpp

@@ -1132,8 +1132,8 @@ gfxHarfBuzzShaper::SetGlyphsFromRun(gfxContext *aContext,
                     : NS_floor(hb2appUnits * x_offset + 0.5);
                 hb_position_t y_offset = posInfo[glyphStart].y_offset;
                 details->mYOffset = yPos -
-                    roundY ? dev2appUnits * FixedToIntRound(y_offset)
-                    : NS_floor(hb2appUnits * y_offset + 0.5);
+                    (roundY ? dev2appUnits * FixedToIntRound(y_offset)
+                     : NS_floor(hb2appUnits * y_offset + 0.5));
 
                 details->mAdvance = advance;
                 hb_position_t y_advance = posInfo[glyphStart].y_advance;