Relanding: Break peerconnection_jni.cc into multiple files, in "pc" directory.

webrtc/sdk/android/src/jni/pc/mediaconstraints_jni.h

+/*
+ *  Copyright 2017 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 WEBRTC_SDK_ANDROID_SRC_JNI_PC_MEDIACONSTRAINTS_JNI_H_
+#define WEBRTC_SDK_ANDROID_SRC_JNI_PC_MEDIACONSTRAINTS_JNI_H_
+
+#include "webrtc/api/mediaconstraintsinterface.h"
+#include "webrtc/sdk/android/src/jni/jni_helpers.h"
+
+namespace webrtc_jni {
+
+// Wrapper for a Java MediaConstraints object.  Copies all needed data so when
+// the constructor returns the Java object is no longer needed.
+class MediaConstraintsJni : public webrtc::MediaConstraintsInterface {
+ public:
+  MediaConstraintsJni(JNIEnv* jni, jobject j_constraints);
+  virtual ~MediaConstraintsJni() {}
+
+  // MediaConstraintsInterface.
+  const Constraints& GetMandatory() const override { return mandatory_; }
+  const Constraints& GetOptional() const override { return optional_; }
+
+ private:
+  // Helper for translating a List<Pair<String, String>> to a Constraints.
+  static void PopulateConstraintsFromJavaPairList(JNIEnv* jni,
+                                                  jobject j_constraints,
+                                                  const char* field_name,
+                                                  Constraints* field);
+
+  Constraints mandatory_;
+  Constraints optional_;
+};
+
+}  // namespace webrtc_jni
+
+#endif  // WEBRTC_SDK_ANDROID_SRC_JNI_PC_MEDIACONSTRAINTS_JNI_H_