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/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index d43d5a4..065aecd 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -2152,11 +2152,13 @@
 
 void SkCanvas::onDrawPosText(const void* text, size_t byteLength, const SkPoint pos[],
                              const SkPaint& paint) {
+    SkPoint textOffset = SkPoint::Make(0, 0);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type, NULL)
 
     while (iter.next()) {
         SkDeviceFilteredPaint dfp(iter.fDevice, looper.paint());
-        iter.fDevice->drawPosText(iter, text, byteLength, &pos->fX, 0, 2,
+        iter.fDevice->drawPosText(iter, text, byteLength, &pos->fX, 2, textOffset,
                                   dfp.paint());
     }
 
@@ -2165,11 +2167,14 @@
 
 void SkCanvas::onDrawPosTextH(const void* text, size_t byteLength, const SkScalar xpos[],
                               SkScalar constY, const SkPaint& paint) {
+
+    SkPoint textOffset = SkPoint::Make(0, constY);
+
     LOOPER_BEGIN(paint, SkDrawFilter::kText_Type, NULL)
 
     while (iter.next()) {
         SkDeviceFilteredPaint dfp(iter.fDevice, looper.paint());
-        iter.fDevice->drawPosText(iter, text, byteLength, xpos, constY, 1,
+        iter.fDevice->drawPosText(iter, text, byteLength, xpos, 1, textOffset,
                                   dfp.paint());
     }