Allow passing in a custom native library loader.

All previous initialize methods are deprecated and a new initialize
that uses a builder pattern is added. This gives us full control over
the order of initialization.

Bug: webrtc:7474
Change-Id: I006190e50f2e75c5015f0be75b86d367676db2cc
Reviewed-on: https://webrtc-review.googlesource.com/4160
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20037}

sdk/android/src/java/org/webrtc/NativeLibrary.java

@@ -0,0 +1,54 @@
+/*
+ *  Copyright (c) 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.
+ */
+
+package org.webrtc;
+
+class NativeLibrary {
+  private static String TAG = "NativeLibrary";
+
+  static class DefaultLoader implements NativeLibraryLoader {
+    @Override
+    public boolean load(String name) {
+      Logging.d(TAG, "Loading library: " + name);
+      try {
+        System.loadLibrary(name);
+      } catch (UnsatisfiedLinkError e) {
+        Logging.e(TAG, "Failed to load native library: " + name, e);
+        return false;
+      }
+      return true;
+    }
+  }
+
+  private static Object lock = new Object();
+  private static boolean libraryLoaded = false;
+
+  /**
+   * Loads the native library. Clients should call PeerConnectionFactory.initialize. It will call
+   * this method for them.
+   */
+  static void initialize(NativeLibraryLoader loader) {
+    synchronized (lock) {
+      if (libraryLoaded) {
+        Logging.d(TAG, "Native library has already been loaded.");
+        return;
+      }
+      Logging.d(TAG, "Loading native library.");
+      libraryLoaded = loader.load("jingle_peerconnection_so");
+    }
+  }
+
+  /** Returns true if the library has been loaded successfully. */
+  static boolean isLoaded() {
+    synchronized (lock) {
+      return libraryLoaded;
+    }
+  }
+}