add peekPixels to SkCanvas and SkSurface

gyp/gmslides.gypi

 # include this gypi to include all the golden master slides.
 {
   'include_dirs': [
     '../gm',
     # include dirs needed by particular GMs
     '../src/utils/debugger',
     '../src/images',
     '../src/lazy',
   ],
   'sources': [
@@ skipping 103 matching lines @@
     '../gm/nonclosedpaths.cpp',
     '../gm/offsetimagefilter.cpp',
     '../gm/optimizations.cpp',
     '../gm/ovals.cpp',
     '../gm/patheffects.cpp',
     '../gm/pathfill.cpp',
     '../gm/pathinterior.cpp',
     '../gm/pathopsinverse.cpp',
     '../gm/pathopsskpclip.cpp',
     '../gm/pathreverse.cpp',
+    '../gm/peekpixels.cpp',
     '../gm/perlinnoise.cpp',
     '../gm/pictureimagefilter.cpp',
     '../gm/points.cpp',
     '../gm/poly2poly.cpp',
     '../gm/polygons.cpp',
     '../gm/quadpaths.cpp',
     '../gm/rects.cpp',
     '../gm/resizeimagefilter.cpp',
     '../gm/rrect.cpp',
     '../gm/rrects.cpp',
@@ skipping 40 matching lines @@
     # Files needed by particular GMs
     '../src/utils/debugger/SkDrawCommand.h',
     '../src/utils/debugger/SkDrawCommand.cpp',
     '../src/utils/debugger/SkDebugCanvas.h',
     '../src/utils/debugger/SkDebugCanvas.cpp',
     '../src/utils/debugger/SkObjectParser.h',
     '../src/utils/debugger/SkObjectParser.cpp',
 
   ],
 }