Reland of Fix android_junit_tests and add a GN target for them.

webrtc/BUILD.gn

Index: webrtc/BUILD.gn
diff --git a/webrtc/BUILD.gn b/webrtc/BUILD.gn
index 88c4e09c72af1cb5e9d56fb3651888a31d32c6c3..d504b836d7e51ee89cb044a2f206f93efe34420f 100644
--- a/webrtc/BUILD.gn
+++ b/webrtc/BUILD.gn
@@ -827,4 +827,15 @@ if (rtc_include_tests) {
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
   }
+
+  if (is_android) {
+    junit_binary("android_junit_tests") {
+      java_files = [ "androidjunit/src/org/webrtc/CameraEnumerationTest.java" ]
+
+      deps = [
+        "//webrtc/api:libjingle_peerconnection_java",
+        "//webrtc/api:libjingle_peerconnection_jni",
+      ]
+    }
+  }
 }