Reland "Android: Generate JNI code for stats"

This reverts commit 43d069a2cdb90ec8c887cf8aa68b42b7cf7ea49d.

Reason for revert: Include fix for local reference overflow.

Original change's description:
> Revert "Android: Generate JNI code for stats"
>
> This reverts commit aede67a199ae0552074bfec4bb03cc9a6a5fba0f.
>
> Reason for revert: Causes error:
> JNI ERROR (app bug): local reference table overflow (max=512)'
>
> Original change's description:
> > Android: Generate JNI code for stats
> >
> > This CL also unifies the functions for converting from C++ to Java, and
> > generates the boiler plate for converting C++ vectors to Java arrays.
> >
> > Bug: webrtc:8278
> > Change-Id: I262e9162beae8a64ba0e8b6a27e1081207b03961
> > Reviewed-on: https://webrtc-review.googlesource.com/26020
> > Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
> > Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
> > Cr-Commit-Position: refs/heads/master@{#20918}
>
> TBR=magjed@webrtc.org,sakal@webrtc.org
>
> Change-Id: Ieb26ed8577bd489a4dd4f7542d16a7d0e11f409f
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: webrtc:8278
> Reviewed-on: https://webrtc-review.googlesource.com/26900
> Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
> Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20926}

TBR=magjed@webrtc.org,sakal@webrtc.org

Change-Id: I6f7097f308098e7922fbf0bed577bd69da4e1c61
Bug: webrtc:8278
Reviewed-on: https://webrtc-review.googlesource.com/26901
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20951}
diff --git a/sdk/android/BUILD.gn b/sdk/android/BUILD.gn
index c7738cc..c7427da 100644
--- a/sdk/android/BUILD.gn
+++ b/sdk/android/BUILD.gn
@@ -42,7 +42,14 @@
 }
 
 generate_jar_jni("generated_external_classes_jni") {
-  classes = [ "java/lang/Integer.class" ]
+  classes = [
+    "java/lang/Integer.class",
+    "java/lang/Double.class",
+    "java/lang/Long.class",
+    "java/lang/Boolean.class",
+    "java/math/BigInteger.class",
+    "java/lang/String.class",
+  ]
   jni_package = ""
   jni_generator_include = "//sdk/android/src/jni/jni_generator_helper.h"
 }
@@ -294,6 +301,8 @@
     "api/org/webrtc/RTCStats.java",
     "api/org/webrtc/RTCStatsCollectorCallback.java",
     "api/org/webrtc/RTCStatsReport.java",
+    "api/org/webrtc/StatsObserver.java",
+    "api/org/webrtc/StatsReport.java",
   ]
   jni_package = ""
   jni_generator_include = "//sdk/android/src/jni/jni_generator_helper.h"
@@ -357,6 +366,7 @@
 
   deps = [
     ":base_jni",
+    ":generated_external_classes_jni",
     ":generated_peerconnection_jni",
     "../..:webrtc_common",
     "../../api/video_codecs:video_codecs_api",