Filter out redundant jumplist updates.

chrome/browser/jumplist_win.cc

Index: chrome/browser/jumplist_win.cc
diff --git a/chrome/browser/jumplist_win.cc b/chrome/browser/jumplist_win.cc
index f1e8a879b115547292fa55884733de91cb83c669..bed6653d6f79b919a736f456698aa8133528ba42 100644
--- a/chrome/browser/jumplist_win.cc
+++ b/chrome/browser/jumplist_win.cc
@@ -13,6 +13,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread.h"
+#include "base/trace_event/trace_event.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/favicon/favicon_service_factory.h"
 #include "chrome/browser/history/top_sites_factory.h"
@@ -46,6 +47,9 @@ using content::BrowserThread;
 
 namespace {
 
+// Delay jumplist updates to allow collapsing of redundant update requests.
+const int kDelayForJumplistUpdateInMS = 3500;
+
 // Append the common switches to each shell link.
 void AppendCommonSwitches(ShellLinkItem* shell_link) {
   const char* kSwitchNames[] = { switches::kUserDataDir };
@@ -440,6 +444,23 @@ void JumpList::OnIncognitoAvailabilityChanged() {
 }
 
 void JumpList::PostRunUpdate() {
+  TRACE_EVENT0("browser", "JumpList::PostRunUpdate");
+  // Initialize the one-shot timer to update the jumplists in a while.
+  // If there is already a request queued then cancel it and post the new
+  // request. This ensures that JumpListUpdates won't happen until there has
+  // been a brief quiet period, thus avoiding update storms.
+  if (timer_.IsRunning()) {
+    timer_.Reset();
+  } else {
+    timer_.Start(FROM_HERE,
+                 base::TimeDelta::FromMilliseconds(kDelayForJumplistUpdateInMS),
+                 this,
+                 &JumpList::DeferredRunUpdate);
+  }
+}
+
+void JumpList::DeferredRunUpdate() {
+  TRACE_EVENT0("browser", "JumpList::DeferredRunUpdate");
   // Check if incognito windows (or normal windows) are disabled by policy.
   IncognitoModePrefs::Availability incognito_availability =
       profile_ ? IncognitoModePrefs::GetAvailability(profile_->GetPrefs())