Android: Use scoped java refs

We currently use raw jobject in our code mixed with sporadic
ScopedLocalRefFrame. This CL moves every jobject into a scoped object,
either local, global, or a parameter. Also, this CL uses the JNI
generation script to generate declaration stubs for the Java->C++
functions so that it no longer becomes possible to mistype them
without getting compilation errors.

TBR=brandt@webrtc.org

Bug: webrtc:8278,webrtc:6969
Change-Id: Ic7bac74a89c11180177d65041086d7db1cdfb516
Reviewed-on: https://webrtc-review.googlesource.com/34655
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21387}

sdk/android/api/org/webrtc/MediaStreamTrack.java

@@ -11,6 +11,7 @@
 package org.webrtc;
 
 /** Java wrapper for a C++ MediaStreamTrackInterface. */
+@JNINamespace("webrtc::jni")
 public class MediaStreamTrack {
   /** Tracks MediaStreamTrackInterface.TrackState */
   public enum State {
@@ -57,36 +58,32 @@ public class MediaStreamTrack {
   }
 
   public String id() {
-    return getNativeId(nativeTrack);
+    return nativeGetId(nativeTrack);
   }
 
   public String kind() {
-    return getNativeKind(nativeTrack);
+    return nativeGetKind(nativeTrack);
   }
 
   public boolean enabled() {
-    return getNativeEnabled(nativeTrack);
+    return nativeGetEnabled(nativeTrack);
   }
 
   public boolean setEnabled(boolean enable) {
-    return setNativeEnabled(nativeTrack, enable);
+    return nativeSetEnabled(nativeTrack, enable);
   }
 
   public State state() {
-    return getNativeState(nativeTrack);
+    return nativeGetState(nativeTrack);
   }
 
   public void dispose() {
     JniCommon.nativeReleaseRef(nativeTrack);
   }
 
-  private static native String getNativeId(long nativeTrack);
-
-  private static native String getNativeKind(long nativeTrack);
-
-  private static native boolean getNativeEnabled(long nativeTrack);
-
-  private static native boolean setNativeEnabled(long nativeTrack, boolean enabled);
-
-  private static native State getNativeState(long nativeTrack);
+  private static native String nativeGetId(long track);
+  private static native String nativeGetKind(long track);
+  private static native boolean nativeGetEnabled(long track);
+  private static native boolean nativeSetEnabled(long track, boolean enabled);
+  private static native State nativeGetState(long track);
 }