Revert of Enable per thread heap on SharedWorker

third_party/WebKit/Source/core/workers/SharedWorkerThread.cpp

Index: third_party/WebKit/Source/core/workers/SharedWorkerThread.cpp
diff --git a/third_party/WebKit/Source/core/workers/SharedWorkerThread.cpp b/third_party/WebKit/Source/core/workers/SharedWorkerThread.cpp
index ba2a737f47d28216024f00211b4820d6feeba8ac..0df8e0d4fe2223910a6872316b5be4c98e47a600 100644
--- a/third_party/WebKit/Source/core/workers/SharedWorkerThread.cpp
+++ b/third_party/WebKit/Source/core/workers/SharedWorkerThread.cpp
@@ -53,7 +53,7 @@ SharedWorkerThread::SharedWorkerThread(
     : WorkerThread(std::move(workerLoaderProxy), workerReportingProxy),
       m_workerBackingThread(
           WorkerBackingThread::create("SharedWorker Thread",
-                                      BlinkGC::PerThreadHeapMode)),
+                                      BlinkGC::MainThreadHeapMode)),
       m_name(name.isolatedCopy()) {}
 
 SharedWorkerThread::~SharedWorkerThread() {}