Add swingworker back to the sdk.

Needed by draw9patch

Change-Id: I677e4ba5230aa5a8bfc1d497ec2381131c3940d7
diff --git a/build/tools.atree b/build/tools.atree
index e628c97..a953e62 100644
--- a/build/tools.atree
+++ b/build/tools.atree
@@ -103,6 +103,7 @@
 framework/org.eclipse.equinox.common_3.4.0.v20080421-2006.jar tools/lib/org.eclipse.equinox.common_3.4.0.v20080421-2006.jar
 framework/org.eclipse.jface_3.4.2.M20090107-0800.jar          tools/lib/org.eclipse.jface_3.4.2.M20090107-0800.jar
 framework/osgi.jar                                            tools/lib/osgi.jar
+framework/swing-worker-1.1.jar                                tools/lib/swing-worker-1.1.jar
 
 # Proguard
 external/proguard/docs/license.html                           tools/proguard/license.html