add helper to create fancy underlines

src/core/SkGlyphCache.h

Index: src/core/SkGlyphCache.h
diff --git a/src/core/SkGlyphCache.h b/src/core/SkGlyphCache.h
index 2f1f417250eda9aae45b62e614eb158afdb37048..66ea243aa1033715fe5e034627f322a67081ada4 100644
--- a/src/core/SkGlyphCache.h
+++ b/src/core/SkGlyphCache.h
@@ -77,6 +77,12 @@ public:
     */
     const void* findImage(const SkGlyph&);
 
+    /** If the advance axis intersects the glyph's path, append the positions scaled and offset
+        to the array (if non-null), and set the count to the updated array length.
+    */
+    void findIntercepts(const SkScalar bounds[2], SkScalar scale, SkScalar xPos,
+                        bool yAxis, SkGlyph* , SkScalar* array, int* count);
+
     /** Return the Path associated with the glyph. If it has not been generated this will trigger
         that.
     */