fix: support typescript 2.4

This fixes one actual runtime bug and improves the type annotations to fix type check errors caught
by Typescript 2.4.

package.json

@@ -77,7 +77,7 @@
     "sortablejs": "^1.5.0-rc1",
     "style-loader": "^0.13.0",
     "ts-loader": "1.3.2",
-    "typescript": "2.3",
+    "typescript": "2.4",
     "webpack": "^2.2.0",
     "webpack-closure-compiler": "^2.1.2"
   }

src/neuroglancer/chunk_manager/backend.ts

@@ -259,7 +259,7 @@ class ChunkPriorityQueue {
   private recentHead = new Chunk();
   constructor(
       private heapOperations: PairingHeapOperations<Chunk>,
-      private linkedListOperations: LinkedListOperations) {
+      private linkedListOperations: LinkedListOperations<Chunk>) {
     linkedListOperations.initializeHead(this.recentHead);
   }
 

src/neuroglancer/datasource/brainmaps/frontend.ts

@@ -370,11 +370,12 @@ export function getChangeStackList(
     chunkManager: ChunkManager, instance: BrainmapsInstance, volumeId: string) {
   return chunkManager.memoize.getUncounted(
       {instance, type: 'brainmaps:getChangeStackList', volumeId}, () => {
-        let promise: Promise<string[]> = makeRequest(instance, {
-                                           method: 'GET',
-                                           path: `/v1beta2/changes/${volumeId}/change_stacks`,
-                                           responseType: 'json'
-                                         }).then(response => parseChangeStackList(response));
+        let promise: Promise<string[]|undefined> =
+            makeRequest(instance, {
+              method: 'GET',
+              path: `/v1beta2/changes/${volumeId}/change_stacks`,
+              responseType: 'json'
+            }).then(response => parseChangeStackList(response));
         const description = `change stacks for ${volumeId}`;
         StatusMessage.forPromise(promise, {
           delay: true,

src/neuroglancer/layer_dialog.ts

@@ -217,7 +217,7 @@ export class LayerDialog extends Overlay {
 
     this.setInfo('Validating volume source...');
     const token = this.volumeCancellationSource = new CancellationTokenSource();
-    getVolume(this.manager.chunkManager, url, token)
+    getVolume(this.manager.chunkManager, url, /*options=*/undefined, token)
         .then(source => {
           if (token.isCanceled) {
             return;

src/neuroglancer/util/linked_list.ts

@@ -14,13 +14,13 @@
  * limitations under the License.
  */
 
-export interface LinkedListOperations {
-  insertAfter: <T>(head: T, x: T) => void;
-  pop: <T>(head: T) => T;
-  insertBefore: <T>(head: T, x: T) => void;
-  front: <T>(head: T) => T | null;
-  back: <T>(head: T) => T | null;
-  iterator: <T>(head: T) => Iterator<T>;
-  reverseIterator: <T>(head: T) => Iterator<T>;
-  initializeHead: <T>(head: T) => void;
+export interface LinkedListOperations<T> {
+  insertAfter: (head: T, x: T) => void;
+  pop: (head: T) => T;
+  insertBefore: (head: T, x: T) => void;
+  front: (head: T) => T | null;
+  back: (head: T) => T | null;
+  iterator: (head: T) => Iterator<T>;
+  reverseIterator: (head: T) => Iterator<T>;
+  initializeHead: (head: T) => void;
 }