Allow same object to appear in one list when parsing V8 array

Fixes #874.

atom/common/native_mate_converters/v8_value_converter.cc

@@ -294,7 +294,10 @@ base::Value* V8ValueConverter::FromV8Array(
     if (!val->HasRealIndexedProperty(i))
       continue;
 
-    base::Value* child = FromV8ValueImpl(state, child_v8, isolate);
+    // When parsing elements in an array, we use a new state so we can have the
+    // same object showed twice in array.
+    FromV8ValueState new_state;
+    base::Value* child = FromV8ValueImpl(&new_state, child_v8, isolate);
     if (child)
       result->Append(child);
     else

spec/api-ipc-spec.coffee

@@ -60,6 +60,14 @@ describe 'ipc module', ->
         done()
       ipc.send 'message', obj
 
+    it 'should work when sending the same object twice in one message', (done) ->
+      obj = key: 'some'
+      ipc.once 'message', (message) ->
+        assert.deepEqual message[0], obj
+        assert.deepEqual message[1], obj
+        done()
+      ipc.send 'message', [obj, obj]
+
   describe 'ipc.sendSync', ->
     it 'can be replied by setting event.returnValue', ->
       msg = ipc.sendSync 'echo', 'test'