Add Platform Independent Eddystone Encoder

components/physical_web/eddystone/eddystone_encoder.h

Index: components/physical_web/eddystone/eddystone_encoder.h
diff --git a/components/physical_web/eddystone/eddystone_encoder.h b/components/physical_web/eddystone/eddystone_encoder.h
new file mode 100644
index 0000000000000000000000000000000000000000..eaff749733cd7a8cc64ba064b380e5fcf46c33b6
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+++ b/components/physical_web/eddystone/eddystone_encoder.h
@@ -0,0 +1,34 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_PHYSICAL_WEB_EDDYSTONE_EDDYSTONE_ENCODER_H_
+#define COMPONENTS_PHYSICAL_WEB_EDDYSTONE_EDDYSTONE_ENCODER_H_
+
+#include <string>
+#include <vector>
+
+namespace physical_web {
+
+const size_t kEmptyUrl = static_cast<size_t>(-1);
+const size_t kInvalidUrl = static_cast<size_t>(-2);
+const size_t kInvalidFormat = static_cast<size_t>(-3);
+const size_t kNullEncodedUrl = static_cast<size_t>(-4);
+
+/*
+ * EncodeUrl takes a URL in the form of a std::string and
+ * a pointer to a uint8_t vector to populate with the eddystone
+ * encoding of the URL.
+ * Returns:
+ *   kEmptyUrl If the URL parameter is empty.
+ *   kInvalidUrl If the URL parameter is not a valid URL.
+ *   kInvalidFormat If the URL parameter is not a standard HTTPS/HTTP URL.
+ *   kNullEncodedUrl If the encoded_url vector is NULL.
+ *   Length of encoded URL.
+ * Eddystone spec can be found here:
+ * https://github.com/google/eddystone/blob/master/protocol-specification.md
+ */
+size_t EncodeUrl(const std::string& url, std::vector<uint8_t>* encoded_url);
+}
+
+#endif  // COMPONENTS_PHYSICAL_WEB_EDDYSTONE_EDDYSTONE_ENCODER_H_