Fix vcall on nullptr in ~Performance.

third_party/WebKit/Source/core/timing/Performance.cpp

Index: third_party/WebKit/Source/core/timing/Performance.cpp
diff --git a/third_party/WebKit/Source/core/timing/Performance.cpp b/third_party/WebKit/Source/core/timing/Performance.cpp
index 608e1c9b2330f0fa74f9548df1d2d18e98863fac..9f2bda47aae307140f6fb95b10fd158b32bf4750 100644
--- a/third_party/WebKit/Source/core/timing/Performance.cpp
+++ b/third_party/WebKit/Source/core/timing/Performance.cpp
@@ -63,6 +63,9 @@ Performance::Performance(LocalFrame* frame)
       m_observingLongTasks(false) {}
 
 Performance::~Performance() {
+  if (!frame()) {
+    return;
+  }
   LocalFrame* localRoot = frame()->localFrameRoot();
   if (m_observingLongTasks && localRoot) {
     m_observingLongTasks = false;