Enable and fix Eclipse warnings about redundant type arguments

Since Java 7 it is possible to replace the type arguments required to
invoke the constructor of a generic class with an empty set of type
parameters (<>) as long as the compiler can infer the type arguments
from the context [1].

Enable the Eclipse warning about redundant type arguments, and remove
the ones it warns about.

[1] http://goo.gl/SG21kM

Change-Id: I422882949a6a6a57391580d881f73120b2843a0e

gerrit-gwtdebug/src/main/java/com/google/gwt/dev/codeserver/WebServer.java

@@ -491,7 +491,7 @@ public class WebServer {
    * by dev_mode_on.js in a JSONP request to "/recompile".)
    */
   private Map<String, String> getBindingProperties(HttpServletRequest request) {
-    Map<String, String> result = new HashMap<String, String>();
+    Map<String, String> result = new HashMap<>();
     for (Object key : request.getParameterMap().keySet()) {
       String propName = (String) key;
       if (!propName.equals("_callback")) {