Revert of add peekPixels to SkCanvas and SkSurface (https://codereview.chromium.org/161733002/)

Reason for revert:
compile issues with gm/xfermodes3

Original issue's description:
> add peekPixels to SkCanvas and SkSurface
>
> clone of https://codereview.chromium.org/159723006/
>
> Committed: https://code.google.com/p/skia/source/detail?r=13427

R=jvanverth@google.com
NOTREECHECKS=true
NOTRY=true

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/163823002

git-svn-id: http://skia.googlecode.com/svn/trunk@13428 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index 15e56a3..53e15a5 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -1128,9 +1128,8 @@
 
 static SkBitmap capture_bitmap(SkCanvas* canvas) {
     SkBitmap bm;
-    if (bm.allocPixels(canvas->imageInfo())) {
-        canvas->readPixels(&bm, 0, 0);
-    }
+    const SkBitmap& src = canvas->getDevice()->accessBitmap(false);
+    src.copyTo(&bm, src.config());
     return bm;
 }