Added JUnit sources.

com.google.eclipse.protobuf.ui.test/META-INF/MANIFEST.MF

diff --git a/com.google.eclipse.protobuf.ui.test/META-INF/MANIFEST.MF b/com.google.eclipse.protobuf.ui.test/META-INF/MANIFEST.MF
index 92a8b48..308f6c5 100644
--- a/com.google.eclipse.protobuf.ui.test/META-INF/MANIFEST.MF
+++ b/com.google.eclipse.protobuf.ui.test/META-INF/MANIFEST.MF
@@ -7,6 +7,7 @@
 Fragment-Host: com.google.eclipse.protobuf.ui;bundle-version="1.0.0"
 Bundle-RequiredExecutionEnvironment: J2SE-1.5
 Require-Bundle: org.junit;bundle-version="4.8.1",
+ org.junit.source;bundle-version="4.8.1",
  org.eclipse.xtext.junit;bundle-version="2.0.0",
  org.eclipse.xtext.junit4;bundle-version="2.0.0",
  org.eclipse.xtext.ui.junit;bundle-version="2.0.0"