Rewrite scoped_ptr<T>(NULL) to use the default ctor in chrome/.

chrome/browser/performance_monitor/performance_monitor.cc

Index: chrome/browser/performance_monitor/performance_monitor.cc
diff --git a/chrome/browser/performance_monitor/performance_monitor.cc b/chrome/browser/performance_monitor/performance_monitor.cc
index 5f805653d5e5520cb90cc5922890388deb5b20f1..643c4c1cca07733275803df8da491aa0e06c7658 100644
--- a/chrome/browser/performance_monitor/performance_monitor.cc
+++ b/chrome/browser/performance_monitor/performance_monitor.cc
@@ -98,9 +98,7 @@ PerformanceMonitor::PerformanceDataForIOThread::PerformanceDataForIOThread()
     : network_bytes_read(0) {
 }
 
-PerformanceMonitor::PerformanceMonitor() : database_(NULL),
-                                           metrics_map_(new MetricsMap) {
-}
+PerformanceMonitor::PerformanceMonitor() : metrics_map_(new MetricsMap) {}
 
 PerformanceMonitor::~PerformanceMonitor() {
   BrowserThread::PostBlockingPoolSequencedTask(