Revert of Revert of Fix SkTextBlob offset semantics.

include/core/SkDevice.h

Index: include/core/SkDevice.h
diff --git a/include/core/SkDevice.h b/include/core/SkDevice.h
index 08320bf7b45f7cfdc4cf6bc3c7065307a6821d27..fb3c206e9eda36fc6a93ee8caff7c896bb40c504 100644
--- a/include/core/SkDevice.h
+++ b/include/core/SkDevice.h
@@ -218,8 +218,8 @@
     virtual void drawText(const SkDraw&, const void* text, size_t len,
                           SkScalar x, SkScalar y, const SkPaint& paint) = 0;
     virtual void drawPosText(const SkDraw&, const void* text, size_t len,
-                             const SkScalar pos[], SkScalar constY,
-                             int scalarsPerPos, const SkPaint& paint) = 0;
+                             const SkScalar pos[], int scalarsPerPos,
+                             const SkPoint& offset, const SkPaint& paint) = 0;
     virtual void drawTextOnPath(const SkDraw&, const void* text, size_t len,
                                 const SkPath& path, const SkMatrix* matrix,
                                 const SkPaint& paint) = 0;