Removing prerender dead code.

chrome/browser/prerender/prerender_manager.cc

Index: chrome/browser/prerender/prerender_manager.cc
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index b43eec6bd94e869a3cf20555003360251379897b..c6f0df70b5313cb29ac2b7beac8a1f0865b10eaa 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -62,10 +62,6 @@ namespace prerender {
 
 namespace {
 
-// Time window for which we will record windowed PLT's from the last
-// observed link rel=prefetch tag.
-const int kWindowDurationSeconds = 30;
-
 // Time interval at which periodic cleanups are performed.
 const int kPeriodicCleanupIntervalMs = 1000;