Add Recent Blocks controller

Tracks recent blocks, useful for estimating recent successful gas
prices.

app/scripts/controllers/recent-blocks.js

@@ -0,0 +1,37 @@
+const ObservableStore = require('obs-store')
+const extend = require('xtend')
+
+class RecentBlocksController {
+
+  constructor (opts = {}) {
+    const { blockTracker } = opts
+    this.blockTracker = blockTracker
+    this.historyLength = opts.historyLength || 40
+
+    const initState = extend({
+      recentBlocks: [],
+    }, opts.initState)
+    this.store = new ObservableStore(initState)
+
+    this.blockTracker.on('block', this.processBlock.bind(this))
+  }
+
+  resetState () {
+    this.store.updateState({
+      recentBlocks: [],
+    })
+  }
+
+  processBlock (newBlock) {
+    const state = this.store.getState()
+    state.recentBlocks.push(newBlock)
+
+    while (state.recentBlocks.length > this.historyLength) {
+      state.recentBlocks.shift()
+    }
+
+    this.store.updateState(state)
+  }
+}
+
+module.exports = RecentBlocksController

app/scripts/metamask-controller.js

@@ -23,6 +23,7 @@ const ShapeShiftController = require('./controllers/shapeshift')
 const AddressBookController = require('./controllers/address-book')
 const InfuraController = require('./controllers/infura')
 const BlacklistController = require('./controllers/blacklist')
+const RecentBlocksController = require('./controllers/recent-blocks')
 const MessageManager = require('./lib/message-manager')
 const PersonalMessageManager = require('./lib/personal-message-manager')
 const TypedMessageManager = require('./lib/typed-message-manager')
@@ -91,6 +92,10 @@ module.exports = class MetamaskController extends EventEmitter {
     this.provider = this.initializeProvider()
     this.blockTracker = this.provider._blockTracker
 
+    this.recentBlocksController = new RecentBlocksController({
+      blockTracker: this.blockTracker,
+    })
+
     // eth data query tools
     this.ethQuery = new EthQuery(this.provider)
     // account tracker watches balances, nonces, and any code at their address.
@@ -196,25 +201,30 @@ module.exports = class MetamaskController extends EventEmitter {
     this.blacklistController.store.subscribe((state) => {
       this.store.updateState({ BlacklistController: state })
     })
+    this.recentBlocksController.store.subscribe((state) => {
+      this.store.updateState({ RecentBlocks: state })
+    })
     this.infuraController.store.subscribe((state) => {
       this.store.updateState({ InfuraController: state })
     })
 
     // manual mem state subscriptions
-    this.networkController.store.subscribe(this.sendUpdate.bind(this))
+    const sendUpdate = this.sendUpdate.bind(this)
-    this.accountTracker.store.subscribe(this.sendUpdate.bind(this))
+    this.networkController.store.subscribe(sendUpdate)
-    this.txController.memStore.subscribe(this.sendUpdate.bind(this))
+    this.accountTracker.store.subscribe(sendUpdate)
-    this.balancesController.store.subscribe(this.sendUpdate.bind(this))
+    this.txController.memStore.subscribe(sendUpdate)
-    this.messageManager.memStore.subscribe(this.sendUpdate.bind(this))
+    this.balancesController.store.subscribe(sendUpdate)
-    this.personalMessageManager.memStore.subscribe(this.sendUpdate.bind(this))
+    this.messageManager.memStore.subscribe(sendUpdate)
-    this.typedMessageManager.memStore.subscribe(this.sendUpdate.bind(this))
+    this.personalMessageManager.memStore.subscribe(sendUpdate)
-    this.keyringController.memStore.subscribe(this.sendUpdate.bind(this))
+    this.typedMessageManager.memStore.subscribe(sendUpdate)
-    this.preferencesController.store.subscribe(this.sendUpdate.bind(this))
+    this.keyringController.memStore.subscribe(sendUpdate)
-    this.addressBookController.store.subscribe(this.sendUpdate.bind(this))
+    this.preferencesController.store.subscribe(sendUpdate)
-    this.currencyController.store.subscribe(this.sendUpdate.bind(this))
+    this.recentBlocksController.store.subscribe(sendUpdate)
-    this.noticeController.memStore.subscribe(this.sendUpdate.bind(this))
+    this.addressBookController.store.subscribe(sendUpdate)
-    this.shapeshiftController.store.subscribe(this.sendUpdate.bind(this))
+    this.currencyController.store.subscribe(sendUpdate)
-    this.infuraController.store.subscribe(this.sendUpdate.bind(this))
+    this.noticeController.memStore.subscribe(sendUpdate)
+    this.shapeshiftController.store.subscribe(sendUpdate)
+    this.infuraController.store.subscribe(sendUpdate)
   }
 
   //
@@ -298,6 +308,7 @@ module.exports = class MetamaskController extends EventEmitter {
       this.currencyController.store.getState(),
       this.noticeController.memStore.getState(),
       this.infuraController.store.getState(),
+      this.recentBlocksController.store.getState(),
       // config manager
       this.configManager.getConfig(),
       this.shapeshiftController.store.getState(),