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..a86017fc674e8385f723bb66203894724e38e784 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("ui", "JumpList::PostRunUpdate");

[gab, 2015/06/11 17:49:23]

Not super familiar with which tracing category means what, but feels this
belongs more in something like "browser" than "ui", WDYT?

(to me "ui" would be related to actually drawing the "ui" where as "browser"
would track background browser work)

+  // 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("ui", "JumpList::DeferredRunUpdate");
   // Check if incognito windows (or normal windows) are disabled by policy.
   IncognitoModePrefs::Availability incognito_availability =
       profile_ ? IncognitoModePrefs::GetAvailability(profile_->GetPrefs())