BitmapTextBatch and BitmapTextBlob

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/eed1dae04932483579b02c10f0706127d3f5d984

Review URL: https://codereview.chromium.org/1011403004
diff --git a/src/gpu/SkGpuDevice.h b/src/gpu/SkGpuDevice.h
index 522cba8..8c3414b 100644
--- a/src/gpu/SkGpuDevice.h
+++ b/src/gpu/SkGpuDevice.h
@@ -219,6 +219,7 @@
     static GrRenderTarget* CreateRenderTarget(GrContext*, SkSurface::Budgeted, const SkImageInfo&,
                                               int sampleCount);
 
+    friend class GrBitmapTextContextB;
     friend class GrTextContext;
     typedef SkBaseDevice INHERITED;
 };