add CORS support to the api

src/main/scala/org/apache/mesos/chronos/scheduler/api/ChronosRestModule.scala

@@ -68,7 +68,9 @@ class ChronosRestModule extends ServletModule {
     bind(classOf[GraphManagementResource]).in(Scopes.SINGLETON)
     bind(classOf[StatsResource]).in(Scopes.SINGLETON)
     bind(classOf[RedirectFilter]).in(Scopes.SINGLETON)
+    bind(classOf[CorsFilter]).in(Scopes.SINGLETON)
     //This filter will redirect to the master if running in HA mode.
+    filter("/*").through(classOf[CorsFilter])
     filter("/*").through(classOf[RedirectFilter])
   }
 }

src/main/scala/org/apache/mesos/chronos/scheduler/api/CorsFilter.scala

@@ -0,0 +1,21 @@
+package org.apache.mesos.chronos.scheduler.api
+
+import java.util.logging.{Level, Logger}
+import javax.servlet._
+import javax.servlet.http.{HttpServletRequest, HttpServletResponse}
+
+class CorsFilter extends Filter {
+  val log = Logger.getLogger(getClass.getName)
+
+  def init(filterConfig: FilterConfig) {}
+  def doFilter(rawRequest: ServletRequest, rawResponse: ServletResponse, chain: FilterChain) {
+    rawResponse match {
+      case response: HttpServletResponse =>
+          log.debug("Adding cors header to api response")
+          response.setHeader("Access-Control-Allow-Origin", "*");
+          chain.doFilter(rawRequest, rawResponse)
+      case _ =>
+    }
+  }
+  def destroy() {}
+}