Tidy DEFINE_(THREAD_SAFE_)STATIC_LOCAL() implementations.

third_party/WebKit/Source/core/layout/LayoutTestHelper.cpp

Index: third_party/WebKit/Source/core/layout/LayoutTestHelper.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTestHelper.cpp b/third_party/WebKit/Source/core/layout/LayoutTestHelper.cpp
index 06ccad5ce8ecced663480da4a992f7ba31e06e72..685e0dd7ef0efe426b23ea5803e1ae947753b072 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTestHelper.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTestHelper.cpp
@@ -32,7 +32,12 @@ void FrameLoaderClientWithParent::detached(FrameDetachType) {
 }
 
 ChromeClient& RenderingTest::chromeClient() const {
-  DEFINE_STATIC_LOCAL(EmptyChromeClient, client, (EmptyChromeClient::create()));
+  // |ChromeClient| contains a weak reference to a |Node| (which derives
+  // from |ScriptWrappable|). That reference is only used for unit testing
+  // purposes and will not accidentally leak between contexts. Consequently,
+  // disable the singleton verification check.
+  DEFINE_STATIC_LOCAL(EmptyChromeClient, client, (EmptyChromeClient::create()),
+                      CheckScriptWrappable::No);
   return client;
 }