add skpdiff tool to compare bitmaps

experimental/skpdiff/skpdiff.gyp

Index: experimental/skpdiff/skpdiff.gyp
diff --git a/experimental/skpdiff/skpdiff.gyp b/experimental/skpdiff/skpdiff.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..5b07a44458fbcf6a7c00a756952707e67ba2ae88
--- /dev/null
+++ b/experimental/skpdiff/skpdiff.gyp
@@ -0,0 +1,35 @@
+# GYP file to build skpdiff.
+#
+# To build on Linux:
+#  ./gyp_skia skpdiff.gyp && make skpdiff
+#
+{
+  'targets': [
+    {
+      'target_name': 'skpdiff',
+      'type': 'executable',
+      'sources': [
+        'main.cpp',
+        'SkImageDiffer.cpp',
+        'SkCLImageDiffer.cpp',
+        'skpdiff_util.cpp',
+      ],
+      'dependencies': [
+        '../../gyp/skia_lib.gyp:skia_lib',
+      ],
+      'link_settings': {
+        'libraries': [
+          '-lOpenCL',
+        ],
+      },
+    },
+  ],
+  'conditions': [
+  ],
+}
+
+# Local Variables:
+# tab-width:2
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=2 shiftwidth=2: