Fix SkTextBlob offset semantics.

src/utils/SkGatherPixelRefsAndRects.h

Index: src/utils/SkGatherPixelRefsAndRects.h
diff --git a/src/utils/SkGatherPixelRefsAndRects.h b/src/utils/SkGatherPixelRefsAndRects.h
index e1e5ccd92e22f55c2756a7b8a10c5fca5f5d1cce..0a4bb5b84c377e18d17b39c4ff8fa3cffb61ac7b 100644
--- a/src/utils/SkGatherPixelRefsAndRects.h
+++ b/src/utils/SkGatherPixelRefsAndRects.h
@@ -195,8 +195,8 @@ protected:
         this->drawRect(draw, bounds, paint);
     }
     virtual void drawPosText(const SkDraw& draw, const void* text, size_t len,
-                             const SkScalar pos[], SkScalar constY,
-                             int scalarsPerPos, const SkPaint& paint) SK_OVERRIDE {
+                             const SkScalar pos[], int scalarsPerPos,
+                             const SkPoint& offset, const SkPaint& paint) SK_OVERRIDE {
         SkBitmap bitmap;
         if (!GetBitmapFromPaint(paint, &bitmap)) {
             return;
@@ -209,18 +209,13 @@ protected:
         // Similar to SkDraw asserts.
         SkASSERT(scalarsPerPos == 1 || scalarsPerPos == 2);
 
-        SkScalar y = scalarsPerPos == 1 ? constY : constY + pos[1];
-
-        SkPoint min, max;
-        min.set(pos[0], y);
-        max.set(pos[0], y);
+        SkPoint min = SkPoint::Make(offset.x() + pos[0],
+                                    offset.y() + (2 == scalarsPerPos ? pos[1] : 0));
+        SkPoint max = min;
 
         for (size_t i = 1; i < len; ++i) {
-            SkScalar x = pos[i * scalarsPerPos];
-            SkScalar y = constY;
-            if (2 == scalarsPerPos) {
-                y += pos[i * scalarsPerPos + 1];
-            }
+            SkScalar x = offset.x() + pos[i * scalarsPerPos];
+            SkScalar y = offset.y() + (2 == scalarsPerPos ? pos[i * 2 + 1] : 0);
 
             min.set(SkMinScalar(x, min.x()), SkMinScalar(y, min.y()));
             max.set(SkMaxScalar(x, max.x()), SkMaxScalar(y, max.y()));