TestingPlatformSupport: register Platform instance correctly

third_party/WebKit/Source/core/dom/IdleDeadlineTest.cpp

Index: third_party/WebKit/Source/core/dom/IdleDeadlineTest.cpp
diff --git a/third_party/WebKit/Source/core/dom/IdleDeadlineTest.cpp b/third_party/WebKit/Source/core/dom/IdleDeadlineTest.cpp
index 068150adce9fb62298c6ff20692c58122d00558f..84004a7ec28b1a9b1670e10a027bb2d840ff799d 100644
--- a/third_party/WebKit/Source/core/dom/IdleDeadlineTest.cpp
+++ b/third_party/WebKit/Source/core/dom/IdleDeadlineTest.cpp
@@ -8,6 +8,7 @@
 #include "public/platform/Platform.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "wtf/CurrentTime.h"
+#include "wtf/PtrUtil.h"
 
 namespace blink {
 namespace {
@@ -75,7 +76,8 @@ TEST_F(IdleDeadlineTest, deadlineInPast) {
 }
 
 TEST_F(IdleDeadlineTest, yieldForHighPriorityWork) {
-  MockPlatform platform;
+  ScopedTestingPlatformSupport<MockPlatform> platform(
+      WTF::makeUnique<MockPlatform>());
 
   IdleDeadline* deadline =
       IdleDeadline::create(1.25, IdleDeadline::CallbackType::CalledWhenIdle);