Revert of Enable per thread heap on ServiceWorker

third_party/WebKit/Source/modules/serviceworkers/ServiceWorkerThread.cpp

Index: third_party/WebKit/Source/modules/serviceworkers/ServiceWorkerThread.cpp
diff --git a/third_party/WebKit/Source/modules/serviceworkers/ServiceWorkerThread.cpp b/third_party/WebKit/Source/modules/serviceworkers/ServiceWorkerThread.cpp
index 55f00c8dc9eaeb55a843c7a2011d552eb2b30dec..59ccc2c997cc971c3a8b01ab344f3d97f90b579a 100644
--- a/third_party/WebKit/Source/modules/serviceworkers/ServiceWorkerThread.cpp
+++ b/third_party/WebKit/Source/modules/serviceworkers/ServiceWorkerThread.cpp
@@ -51,7 +51,7 @@ ServiceWorkerThread::ServiceWorkerThread(
     : WorkerThread(std::move(workerLoaderProxy), workerReportingProxy),
       m_workerBackingThread(
           WorkerBackingThread::create("ServiceWorker Thread",
-                                      BlinkGC::PerThreadHeapMode)) {}
+                                      BlinkGC::MainThreadHeapMode)) {}
 
 ServiceWorkerThread::~ServiceWorkerThread() {}