🐎 Use JSON.stringify to serialize state

src/atom-environment.coffee

@@ -813,12 +813,17 @@ class AtomEnvironment extends Model
 
   saveState: ->
     return Promise.resolve() unless @enablePersistence
-    state = @serialize()
 
-    if storageKey = @getStateKey(@project?.getPaths())
-      @stateStore.save(storageKey, state)
-    else
-      @applicationDelegate.setTemporaryWindowState(state)
+    new Promise (resolve, reject) =>
+      window.requestIdleCallback =>
+        state = @serialize()
+        savePromise =
+          if storageKey = @getStateKey(@project?.getPaths())
+            @stateStore.save(storageKey, state)
+          else
+            @applicationDelegate.setTemporaryWindowState(state)
+        savePromise.catch(reject).then(resolve)
+
 
   loadState: ->
     if @enablePersistence

src/state-store.js

@@ -24,18 +24,19 @@ class StateStore {
   }
 
   save (key, value) {
+    // Serialize values using JSON.stringify, as it seems way faster than IndexedDB structured clone.
+    // (Ref.: https://bugs.chromium.org/p/chromium/issues/detail?id=536620)
+    let jsonValue = JSON.stringify(value)
     return new Promise((resolve, reject) => {
-      window.requestIdleCallback(deadline => {
-        this.dbPromise.then(db => {
-          if (db == null) resolve()
+      this.dbPromise.then(db => {
+        if (db == null) resolve()
 
-          var request = db.transaction(['states'], 'readwrite')
-            .objectStore('states')
-            .put({value: value, storedAt: new Date().toString()}, key)
+        var request = db.transaction(['states'], 'readwrite')
+          .objectStore('states')
+          .put({value: jsonValue, storedAt: new Date().toString(), isJSON: true}, key)
 
-          request.onsuccess = resolve
-          request.onerror = reject
-        })
+        request.onsuccess = resolve
+        request.onerror = reject
       })
     })
   }
@@ -51,7 +52,12 @@ class StateStore {
 
         request.onsuccess = (event) => {
           let result = event.target.result
-          resolve(result ? result.value : null)
+          if (result) {
+            // TODO: remove this when state will be serialized only via JSON.
+            resolve(result.isJSON ? JSON.parse(result.value) : result.value)
+          } else {
+            resolve(null)
+          }
         }
 
         request.onerror = (event) => reject(event)