Ensure that performance.memory is updated on first access.

Source/core/timing/MemoryInfo.cpp

Index: Source/core/timing/MemoryInfo.cpp
diff --git a/Source/core/timing/MemoryInfo.cpp b/Source/core/timing/MemoryInfo.cpp
index d5466ee33fa0f79995d904e942063074d994c33c..e0b28c6ca85c412077d134fd6eb9a3ae7b31a0e9 100644
--- a/Source/core/timing/MemoryInfo.cpp
+++ b/Source/core/timing/MemoryInfo.cpp
@@ -42,11 +42,13 @@
 
 namespace blink {
 
+static const double TwentyMinutesInSeconds = 20 * 60;
+
 class HeapSizeCache {
     WTF_MAKE_NONCOPYABLE(HeapSizeCache); WTF_MAKE_FAST_ALLOCATED;
 public:
     HeapSizeCache()
-        : m_lastUpdateTime(0)
+        : m_lastUpdateTime(monotonicallyIncreasingTime() - TwentyMinutesInSeconds)
     {
     }
 
@@ -67,8 +69,6 @@ private:
     {
         // We rate-limit queries to once every twenty minutes to make it more difficult
         // for attackers to compare memory usage before and after some event.
-        const double TwentyMinutesInSeconds = 20 * 60;
-
         double now = monotonicallyIncreasingTime();
         if (now - m_lastUpdateTime >= TwentyMinutesInSeconds) {
             update();