Move rtc_json code from API dir, enable unit test, unmark testonly

This change does three things:
 - Move rtc_json into rtc_base/strings/, a non-API directory more fitting to
   its purpose.
 - Make a target for the currently unused json_unittest.
 - Make the code available for use in non-test code again.

Bug: webrtc:9802
Change-Id: Id964a8a4b47b732a962a364894a4dbd3e7f4650f
Reviewed-on: https://webrtc-review.googlesource.com/103126
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24932}

rtc_base/strings/json.h

@@ -0,0 +1,88 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef RTC_BASE_STRINGS_JSON_H_
+#define RTC_BASE_STRINGS_JSON_H_
+
+#include <string>
+#include <vector>
+
+#if !defined(WEBRTC_EXTERNAL_JSON)
+#include "json/json.h"
+#else
+#include "third_party/jsoncpp/json.h"
+#endif
+
+namespace rtc {
+
+///////////////////////////////////////////////////////////////////////////////
+// JSON Helpers
+///////////////////////////////////////////////////////////////////////////////
+
+// Robust conversion operators, better than the ones in JsonCpp.
+bool GetIntFromJson(const Json::Value& in, int* out);
+bool GetUIntFromJson(const Json::Value& in, unsigned int* out);
+bool GetStringFromJson(const Json::Value& in, std::string* out);
+bool GetBoolFromJson(const Json::Value& in, bool* out);
+bool GetDoubleFromJson(const Json::Value& in, double* out);
+
+// Pull values out of a JSON array.
+bool GetValueFromJsonArray(const Json::Value& in, size_t n, Json::Value* out);
+bool GetIntFromJsonArray(const Json::Value& in, size_t n, int* out);
+bool GetUIntFromJsonArray(const Json::Value& in, size_t n, unsigned int* out);
+bool GetStringFromJsonArray(const Json::Value& in, size_t n, std::string* out);
+bool GetBoolFromJsonArray(const Json::Value& in, size_t n, bool* out);
+bool GetDoubleFromJsonArray(const Json::Value& in, size_t n, double* out);
+
+// Convert json arrays to std::vector
+bool JsonArrayToValueVector(const Json::Value& in,
+                            std::vector<Json::Value>* out);
+bool JsonArrayToIntVector(const Json::Value& in, std::vector<int>* out);
+bool JsonArrayToUIntVector(const Json::Value& in,
+                           std::vector<unsigned int>* out);
+bool JsonArrayToStringVector(const Json::Value& in,
+                             std::vector<std::string>* out);
+bool JsonArrayToBoolVector(const Json::Value& in, std::vector<bool>* out);
+bool JsonArrayToDoubleVector(const Json::Value& in, std::vector<double>* out);
+
+// Convert std::vector to json array
+Json::Value ValueVectorToJsonArray(const std::vector<Json::Value>& in);
+Json::Value IntVectorToJsonArray(const std::vector<int>& in);
+Json::Value UIntVectorToJsonArray(const std::vector<unsigned int>& in);
+Json::Value StringVectorToJsonArray(const std::vector<std::string>& in);
+Json::Value BoolVectorToJsonArray(const std::vector<bool>& in);
+Json::Value DoubleVectorToJsonArray(const std::vector<double>& in);
+
+// Pull values out of a JSON object.
+bool GetValueFromJsonObject(const Json::Value& in,
+                            const std::string& k,
+                            Json::Value* out);
+bool GetIntFromJsonObject(const Json::Value& in,
+                          const std::string& k,
+                          int* out);
+bool GetUIntFromJsonObject(const Json::Value& in,
+                           const std::string& k,
+                           unsigned int* out);
+bool GetStringFromJsonObject(const Json::Value& in,
+                             const std::string& k,
+                             std::string* out);
+bool GetBoolFromJsonObject(const Json::Value& in,
+                           const std::string& k,
+                           bool* out);
+bool GetDoubleFromJsonObject(const Json::Value& in,
+                             const std::string& k,
+                             double* out);
+
+// Writes out a Json value as a string.
+std::string JsonValueToString(const Json::Value& json);
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_STRINGS_JSON_H_