Factor out gin::IsolateHolder's constructor

third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp b/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
index a0c4d830b0038274700ce939d2a12684a327e4e6..13363387953dd7545130493ec32294f3936291ad 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
@@ -397,9 +397,17 @@ void V8Initializer::initializeMainThread() {
   // throttled and memory usage goes up. For now we're using loading task queue
   // to prevent this.
   // TODO(altimin): Consider switching to timerTaskRunner here.
-  v8::Isolate* isolate = V8PerIsolateData::initialize(
+
+  WebTaskRunner* taskRunner =
       scheduler ? scheduler->loadingTaskRunner()
-                : Platform::current()->currentThread()->getWebTaskRunner());
+                : Platform::current()->currentThread()->getWebTaskRunner();
+  std::unique_ptr<gin::IsolateHolder> isolateHolder(
+      WTF::makeUnique<gin::IsolateHolder>(
+          taskRunner ? taskRunner->toSingleThreadTaskRunner() : nullptr,
+          gin::IsolateHolder::kSingleThread,
+          isMainThread() ? gin::IsolateHolder::kDisallowAtomicsWait
+                         : gin::IsolateHolder::kAllowAtomicsWait));
+  v8::Isolate* isolate = V8PerIsolateData::initialize(std::move(isolateHolder));
 
   initializeV8Common(isolate);