SkPDF: move all pdf sources into src/pdf

src/pdf/SkPDFDocument.h

Index: src/pdf/SkPDFDocument.h
diff --git a/src/pdf/SkPDFDocument.h b/src/pdf/SkPDFDocument.h
new file mode 100644
index 0000000000000000000000000000000000000000..8ed76778fe91b8fb79f466967bf50af9f56d5e0d
--- /dev/null
+++ b/src/pdf/SkPDFDocument.h
@@ -0,0 +1,18 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef SkPDFDocument_DEFINED
+#define SkPDFDocument_DEFINED
+
+#include "SkDocument.h"
+
+sk_sp<SkDocument> SkPDFMakeDocument(
+        SkWStream* stream,
+        void (*doneProc)(SkWStream*, bool),
+        SkScalar rasterDpi,
+        SkPixelSerializer* jpegEncoder);
+
+#endif  // SkPDFDocument_DEFINED