Revert of Revert of Fix SkTextBlob offset semantics. (patchset #1 id:1 of https://codereview.chromium.org/609223003/)

Reason for revert:
Re-landing: Chromium-side fix to be landed with the roll (https://codereview.chromium.org/607853003/)

Original issue's description:
> Revert of Fix SkTextBlob offset semantics. (patchset #2 id:20001 of https://codereview.chromium.org/605533002/)
>
> Reason for revert:
> Breaking the Chrome builds with the error:
>
> [14:54:14.317833] ../../skia/ext/pixel_ref_utils.cc:221:16: error: 'drawPosText' marked 'override' but does not override any member functions
> [14:54:14.318022]   virtual void drawPosText(const SkDraw& draw,
> [14:54:14.318082]                ^
>
> Original issue's description:
> > Fix SkTextBlob offset semantics.
> >
> > Implement proper x/y drawTextBlob() handling by plumbing a
> > drawPosText() offset parameter (to act as an additional glyph pos
> > translation) throughout the device layer.
> >
> > The new offset superceeds the existing constY, with a minor semantic
> > tweak: whereas previous implementations were ignoring constY in 2D
> > positioning mode (scalarsPerGlyph == 2), now the offset is always
> > observed, in all positioning modes. We can do this because existing
> > drawPosText() clients always pass constY == 0 for full positioning mode.
> >
> > R=reed@google.com, jvanverth@google.com, robertphillips@google.com
> >
> > Committed: https://skia.googlesource.com/skia/+/c13bc571d3e61a43b87eb97f0719abd304cafaf2
>
> TBR=jvanverth@google.com,reed@google.com,bsalomon@google.com,fmalita@chromium.org
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://skia.googlesource.com/skia/+/d46b8d2bab7cfba8458432248e1568ac377429e9

R=jvanverth@google.com, reed@google.com, bsalomon@google.com, robertphillips@google.com
TBR=bsalomon@google.com, jvanverth@google.com, reed@google.com, robertphillips@google.com
NOTREECHECKS=true
NOTRY=true

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/607413003
diff --git a/src/utils/SkDeferredCanvas.cpp b/src/utils/SkDeferredCanvas.cpp
index c8402dd..06f7bb0 100644
--- a/src/utils/SkDeferredCanvas.cpp
+++ b/src/utils/SkDeferredCanvas.cpp
@@ -210,8 +210,8 @@
                             SkScalar x, SkScalar y, const SkPaint& paint) SK_OVERRIDE
         {SkASSERT(0);}
     virtual void drawPosText(const SkDraw&, 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
         {SkASSERT(0);}
     virtual void drawTextOnPath(const SkDraw&, const void* text,
                                 size_t len, const SkPath& path,
diff --git a/src/utils/SkGatherPixelRefsAndRects.h b/src/utils/SkGatherPixelRefsAndRects.h
index e1e5ccd..0a4bb5b 100644
--- a/src/utils/SkGatherPixelRefsAndRects.h
+++ b/src/utils/SkGatherPixelRefsAndRects.h
@@ -195,8 +195,8 @@
         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 @@
         // 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()));
diff --git a/src/utils/SkPictureUtils.cpp b/src/utils/SkPictureUtils.cpp
index 4f4d2bf..391e5ff 100644
--- a/src/utils/SkPictureUtils.cpp
+++ b/src/utils/SkPictureUtils.cpp
@@ -132,8 +132,8 @@
         this->addBitmapFromPaint(paint);
     }
     virtual void drawPosText(const SkDraw&, const void* text, size_t len,
-                             const SkScalar pos[], SkScalar constY,
-                             int, const SkPaint& paint) SK_OVERRIDE {
+                             const SkScalar pos[], int,
+                             const SkPoint&, const SkPaint& paint) SK_OVERRIDE {
         this->addBitmapFromPaint(paint);
     }
     virtual void drawTextOnPath(const SkDraw&, const void* text, size_t len,