Tested against code to play nice with unit tests.

app/scripts/lib/controllers/preferences.js

@@ -25,6 +25,14 @@ class PreferencesController {
     return this.store.getState().selectedAddress
   }
 
+  updateFrequentRpcList (_url) {
+    return this.addToFrequentRpcList(_url)
+      .then((rpcList) => {
+        this.store.updateState({ frequentRpcList: rpcList })
+        return rpcList
+      })
+  }
+
   addToFrequentRpcList (_url) {
     let rpcList = this.getFrequentRpcList()
     let index = rpcList.findIndex((element) => { return element === _url })
@@ -37,8 +45,7 @@ class PreferencesController {
     if (rpcList.length > 2) {
       rpcList.shift()
     }
-    this.store.updateState({ frequentRpcList: rpcList })
-    return Promise.resolve()
+    return Promise.resolve(rpcList)
   }
 
   getFrequentRpcList () {
@@ -49,6 +56,8 @@ class PreferencesController {
   // PRIVATE METHODS
   //
 
+
+
 }
 
 module.exports = PreferencesController

app/scripts/metamask-controller.js

@@ -259,7 +259,7 @@ module.exports = class MetamaskController extends EventEmitter {
 
       // PreferencesController
       setSelectedAddress:        nodeify(preferencesController.setSelectedAddress).bind(preferencesController),
-      addToFrequentRpcList:      nodeify(preferencesController.addToFrequentRpcList).bind(preferencesController),
+      updateFrequentRpcList:      nodeify(preferencesController.updateFrequentRpcList).bind(preferencesController),
 
       // KeyringController
       setLocked:                 nodeify(keyringController.setLocked).bind(keyringController),

test/unit/actions/config_test.js

@@ -11,6 +11,7 @@ describe ('config view actions', function() {
   var initialState = {
     metamask: {
       rpcTarget: 'foo',
+      frequentRpcList: []
     },
     appState: {
       currentView: {
@@ -30,15 +31,36 @@ describe ('config view actions', function() {
   describe('SET_RPC_TARGET', function() {
 
     it('sets the state.metamask.rpcTarget property of the state to the action.value', function() {
+      const value = {
+        rpcTarget: 'foo',
+        frequentRpcList: ['foo']
+      }
       const action = {
         type: actions.SET_RPC_TARGET,
-        value: 'bar',
+        value,
       }
 
       var result = reducers(initialState, action)
       assert.equal(result.metamask.provider.type, 'rpc')
-      assert.equal(result.metamask.provider.rpcTarget, action.value)
+      assert.equal(result.metamask.provider.rpcTarget, value.rpcTarget)
+      assert.equal(result.metamask.frequentRpcList[0], value.frequentRpcList[0])
     })
+
+    it('should handle multiple requests to change the rpc gracefully', function() {
+      const value = {
+        rpcTarget: 'foo',
+        frequentRpcList: ['foo']
+      }
+
+      const action = {
+        type: actions.SET_RPC_TARGET,
+        value,
+      }
+
+      var result = reducers(initialState, action)
+      var secondResult = reducers(result, action)
+      assert.equal(secondResult.metamask.frequentRpcList.length, 1)
     })
   })
 
+})

ui/app/actions.js

@@ -626,13 +626,19 @@ function markAccountsFound() {
 //
 
 function setRpcTarget (newRpc) {
+  return (dispatch) => {
     if (global.METAMASK_DEBUG) console.log(`background.setRpcTarget`)
-  background.addToFrequentRpcList(newRpc, () => {
     background.setRpcTarget(newRpc)
-  })
-  return {
+    background.updateFrequentRpcList(newRpc, (frequentRpcList) => {
+      const value = {
+        rpcTarget: newRpc,
+        frequentRpcList,
+      }
+      dispatch({
         type: actions.SET_RPC_TARGET,
-    value: newRpc,
+        value,
+      })
+    })
   }
 }
 

ui/app/app.js

@@ -257,7 +257,9 @@ App.prototype.renderNetworkDropdown = function () {
     h(DropMenuItem, {
       label: 'Localhost 8545',
       closeMenu: () => this.setState({ isNetworkMenuOpen: false }),
-      action: () => props.dispatch(actions.setRpcTarget('http://localhost:8545')),
+      action: () => {
+        props.dispatch(actions.setRpcTarget('http://localhost:8545'))
+      },
       icon: h('i.fa.fa-question-circle.fa-lg'),
       activeNetworkRender: props.provider.rpcTarget,
     }),

ui/app/reducers/metamask.js

@@ -55,9 +55,10 @@ function reduceMetamask (state, action) {
 
     case actions.SET_RPC_TARGET:
       return extend(metamaskState, {
+        frequentRpcList: action.value.frequentRpcList,
         provider: {
           type: 'rpc',
-          rpcTarget: action.value,
+          rpcTarget: action.value.rpcTarget,
         },
       })