Add explicit type parameters for typescript 3.4 (#1656)

* Add explicit type parameters for typescript 3.4

* [AUTOMATED]: Prettier Code Styling

Author: Feiyang1

packages/firestore/src/local/lru_garbage_collector.ts

@@ -433,7 +433,7 @@ export class LruGarbageCollector {
           log.debug('LruGarbageCollector', desc);
         }
 
-        return PersistencePromise.resolve({
+        return PersistencePromise.resolve<LruResults>({
           didRun: true,
           sequenceNumbersCollected: sequenceNumbersToCollect,
           targetsRemoved,

packages/firestore/src/local/persistence_promise.ts

@@ -207,7 +207,9 @@ export class PersistencePromise<T> {
   static or(
     predicates: Array<() => PersistencePromise<boolean>>
   ): PersistencePromise<boolean> {
-    let p: PersistencePromise<boolean> = PersistencePromise.resolve(false);
+    let p: PersistencePromise<boolean> = PersistencePromise.resolve<boolean>(
+      false
+    );
     for (const predicate of predicates) {
       p = p.next(isTrue => {
         if (isTrue) {