add peekPixels to SkCanvas and SkSurface

fix reference to SkBaseDevice, which was only a problem in no-gpu build

This reverts commit 4fa44a6bf73891b21917fb90d02beef9143bffa3.

R=reed@google.com

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/163603003

git-svn-id: http://skia.googlecode.com/svn/trunk@13432 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleLayers.cpp b/samplecode/SampleLayers.cpp
index 483943d..bc8b873 100644
--- a/samplecode/SampleLayers.cpp
+++ b/samplecode/SampleLayers.cpp
@@ -42,10 +42,10 @@
     SkCanvas::LayerIter iter(canvas, true);
     int index = 0;
     while (!iter.done()) {
-        const SkBitmap& bm = iter.device()->accessBitmap(false);
+        SkImageInfo info = iter.device()->imageInfo();
         const SkIRect& clip = iter.clip().getBounds();
         SkDebugf("Layer[%d] bitmap [%d %d] X=%d Y=%d clip=[%d %d %d %d] alpha=%d\n", index++,
-                 bm.width(), bm.height(), iter.x(), iter.y(),
+                 info.width(), info.height(), iter.x(), iter.y(),
                  clip.fLeft, clip.fTop, clip.fRight, clip.fBottom,
                  iter.paint().getAlpha());
         iter.next();