Deprecate ContextUtils.getApplicationContext.

Allows passing in the application context to NetworkMonitor in
startMonitoring. The audio code will refactored once it is moved under
sdk/android.

Bug: webrtc:8937
Change-Id: I50c917a845fc4f711899a97d34c04813cc68b68c
Reviewed-on: https://webrtc-review.googlesource.com/58091
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22231}

rtc_base/java/src/org/webrtc/ContextUtils.java

@@ -36,7 +36,10 @@ public class ContextUtils {
 
   /**
    * Returns the stored application context.
+   *
+   * @deprecated crbug.com/webrtc/8937
    */
+  @Deprecated
   public static Context getApplicationContext() {
     return applicationContext;
   }