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/tools/debugger/SkDrawCommand.cpp b/tools/debugger/SkDrawCommand.cpp
index 3bb1b90..09b8ab4 100644
--- a/tools/debugger/SkDrawCommand.cpp
+++ b/tools/debugger/SkDrawCommand.cpp
@@ -313,7 +313,7 @@
 namespace {
 
 void xlate_and_scale_to_bounds(SkCanvas* canvas, const SkRect& bounds) {
-    const SkISize& size = canvas->getDeviceSize();
+    const SkISize& size = canvas->getBaseLayerSize();
 
     static const SkScalar kInsetFrac = 0.9f; // Leave a border around object
 
@@ -348,7 +348,7 @@
 }
 
 void render_bitmap(SkCanvas* canvas, const SkBitmap& input, const SkRect* srcRect = nullptr) {
-    const SkISize& size = canvas->getDeviceSize();
+    const SkISize& size = canvas->getBaseLayerSize();
 
     SkScalar xScale = SkIntToScalar(size.fWidth-2) / input.width();
     SkScalar yScale = SkIntToScalar(size.fHeight-2) / input.height();