More distance field improvements:
- Make sure we only use the 0,0 subpixel glyph
- Copy image data into outsized buffer to ensure we capture outer edges
- Change edge dump to blend better with original glyph
- Edges are detected across >128 and <128 boundaries, or when
  there are two non-zero <128 pixels next to each other

BUG=skia:
R=robertphillips@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/208893003

git-svn-id: http://skia.googlecode.com/svn/trunk@13916 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index 2163e64..1a422c6 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -372,7 +372,7 @@
     SkFixed fy = SkScalarToFixed(y) + SK_FixedHalf;
     SkFixed fixedScale = SkScalarToFixed(sizeRatio);
     while (text < stop) {
-        const SkGlyph& glyph = glyphCacheProc(cache, &text, fx, fy);
+        const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
 
         if (glyph.fWidth) {
             this->drawPackedGlyph(GrGlyph::Pack(glyph.getGlyphID(),