Separate and update PDF_DIFF_TRACE_IN_PNG

experimental/PdfViewer/inc/SkPdfDiffEncoder.h

Index: experimental/PdfViewer/inc/SkPdfDiffEncoder.h
diff --git a/experimental/PdfViewer/inc/SkPdfDiffEncoder.h b/experimental/PdfViewer/inc/SkPdfDiffEncoder.h
new file mode 100644
index 0000000000000000000000000000000000000000..118f9c9f77156a799ff051526909207dadac5b7a
--- /dev/null
+++ b/experimental/PdfViewer/inc/SkPdfDiffEncoder.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPdfDiffEncoder_DEFINED
+#define SkPdfDiffEncoder_DEFINED
+
+struct PdfToken;
+
+class SkPdfDiffEncoder {
+public:
+    // If PDF_TRACE_DIFF_IN_PNG is defined, the difference created by
+    // using this token is written to a file named
+    // "/tmp/log_step_by_step/step-%i-%s.png". Otherwise this function does
+    // nothing.
+    // TODO(scroggo): Pass SkPdfContext and SkCanvas for info.
+    static void WriteToFile(PdfToken*);

[mtklein, 2013/11/22 14:46:12]

Do you anticipate this class will become more than just a function?

If not, or at least not for now, I'd just change this to

namespace SkPdfDiffEncoder {
void WriteToFile(PdfToken*);
}

to make it clear SkPdfDiffEncoder is a namespace.  I don't think the callers
would have to change at all.

[scroggo, 2013/11/22 15:47:16]

reed@ encouraged me to use a class in another instance  for consistency- see
(https://codereview.chromium.org/25581002/diff/1/include/utils/SkFrontBuffered...).

As discussed in person, I think we're content to do either one.

+};
+
+#endif // SkPdfDiffEncoder_DEFINED