Bug 1480951 - Make SessionStore respect sessionStorage.clear(). r=mikedeboer

Differential Revision: https://phabricator.services.mozilla.com/D5066

--HG--
extra : rebase_source : 447e78988d9657247b6870a68dc57bc066905092

browser/components/sessionstore/ContentSessionStore.jsm

@@ -524,7 +524,15 @@ class SessionStorageListener extends Handler {
     if (!this._changes[domain]) {
       this._changes[domain] = {};
     }
-    this._changes[domain][key] = newValue;
+
+    // If the key isn't defined, then .clear() was called, and we send
+    // up null for this domain to indicate that storage has been cleared
+    // for it.
+    if (!key) {
+      this._changes[domain] = null;
+    } else {
+      this._changes[domain][key] = newValue;
+    }
 
     this.messageQueue.push("storagechange", () => {
       let tmp = this._changes;

browser/components/sessionstore/TabStateCache.jsm

@@ -77,17 +77,23 @@ var TabStateCacheInternal = {
 
     let storage = data.storage;
     for (let domain of Object.keys(change)) {
-      for (let key of Object.keys(change[domain])) {
-        let value = change[domain][key];
-        if (value === null) {
-          if (storage[domain] && storage[domain][key]) {
-            delete storage[domain][key];
+      if (!change[domain]) {
+        // We were sent null in place of the change object, which means
+        // we should delete session storage entirely for this domain.
+        delete storage[domain];
+      } else {
+        for (let key of Object.keys(change[domain])) {
+          let value = change[domain][key];
+          if (value === null) {
+            if (storage[domain] && storage[domain][key]) {
+              delete storage[domain][key];
+            }
+          } else {
+            if (!storage[domain]) {
+              storage[domain] = {};
+            }
+            storage[domain][key] = value;
           }
-        } else {
-          if (!storage[domain]) {
-            storage[domain] = {};
-          }
-          storage[domain][key] = value;
         }
       }
     }