Bind Window focus ability to the ExecutionContext instead of the process.

Source/modules/serviceworkers/WaitUntilObserver.cpp

Index: Source/modules/serviceworkers/WaitUntilObserver.cpp
diff --git a/Source/modules/serviceworkers/WaitUntilObserver.cpp b/Source/modules/serviceworkers/WaitUntilObserver.cpp
index 28359e332684f192ecfa75cd111a5db9cf2b7cb6..d03bf9e79f1622e55a09b74f975d34460a5ceeea 100644
--- a/Source/modules/serviceworkers/WaitUntilObserver.cpp
+++ b/Source/modules/serviceworkers/WaitUntilObserver.cpp
@@ -88,6 +88,16 @@ void WaitUntilObserver::waitUntil(ScriptState* scriptState, const ScriptValue& v
         return;
     }
 
+    if (!executionContext())
+        return;
+
+    // When handling a notificationclick event, we want to allow one window to
+    // be focused. Regardless of whether one window was focused,
+    // |consumeWindowFocus| will be called when all the pending activities will
+    // be resolved.
+    if (m_type == NotificationClick)
+        executionContext()->allowWindowFocus();
+
     incrementPendingActivity();
     ScriptPromise::cast(scriptState, value).then(
         ThenFunction::createFunction(scriptState, this, ThenFunction::Fulfilled),
@@ -134,6 +144,7 @@ void WaitUntilObserver::decrementPendingActivity()
         break;
     case NotificationClick:
         client->didHandleNotificationClickEvent(m_eventID, result);
+        executionContext()->consumeWindowFocus();
         break;
     case Push:
         client->didHandlePushEvent(m_eventID, result);