Initial change to move text blob to GrTextContext

BUG=skia:

Review URL: https://codereview.chromium.org/1019633002
diff --git a/src/gpu/SkGpuDevice.h b/src/gpu/SkGpuDevice.h
index be7857a..c712ca9 100644
--- a/src/gpu/SkGpuDevice.h
+++ b/src/gpu/SkGpuDevice.h
@@ -99,6 +99,8 @@
     virtual void drawPosText(const SkDraw&, const void* text, size_t len,
                              const SkScalar pos[], int scalarsPerPos,
                              const SkPoint& offset, const SkPaint&) SK_OVERRIDE;
+    virtual void drawTextBlob(const SkDraw&, const SkTextBlob*, SkScalar x, SkScalar y,
+                              const SkPaint& paint, SkDrawFilter* drawFilter) SK_OVERRIDE;
     virtual void drawVertices(const SkDraw&, SkCanvas::VertexMode, int vertexCount,
                               const SkPoint verts[], const SkPoint texs[],
                               const SkColor colors[], SkXfermode* xmode,