hide trivial helpers on canvas

BUG=skia:

Change-Id: I42d4ca92897bde5bd8e0575a0104b12b83134cef
Reviewed-on: https://skia-review.googlesource.com/8852
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/samplecode/SampleClipDrawMatch.cpp b/samplecode/SampleClipDrawMatch.cpp
index ea30cc6..b2158a6 100644
--- a/samplecode/SampleClipDrawMatch.cpp
+++ b/samplecode/SampleClipDrawMatch.cpp
@@ -204,7 +204,7 @@
             } break;
         }
 
-        SkISize size = canvas->getDeviceSize();
+        SkISize size = canvas->getBaseLayerSize();
         SkRect bigR = SkRect::MakeWH(SkIntToScalar(size.width()), SkIntToScalar(size.height()));
 
         SkPaint p;