Filter out redundant jumplist updates.

chrome/browser/jumplist_win.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/jumplist_win.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/files/file_util.h"
@@ skipping 28 matching lines @@
 #include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/favicon_size.h"
 #include "ui/gfx/icon_util.h"
 #include "ui/gfx/image/image_family.h"
 #include "url/gurl.h"
 
 using content::BrowserThread;
 
 namespace {
 
+// Delay jumplist update tasks to allow collapsing of redundant
+// update requests.
+const int kDelayMSForJumplistUpdate = 1500;

[jochen (gone - plz use gerrit), 2015/03/31 10:28:52]

nit. it's more common to have the unit last (kDelayForJumplistUpdateInMS)

[brucedawson, 2015/06/03 17:57:16]

Done.

+
 // Append the common switches to each shell link.
 void AppendCommonSwitches(ShellLinkItem* shell_link) {
   const char* kSwitchNames[] = { switches::kUserDataDir };
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   shell_link->GetCommandLine()->CopySwitchesFrom(command_line,
                                                  kSwitchNames,
                                                  arraysize(kSwitchNames));
 }
 
@@ skipping 379 matching lines @@
   // If |icon_urls_| isn't empty then OnFaviconDataAvailable will eventually
   // call PostRunUpdate().
 }
 
 void JumpList::PostRunUpdate() {
   // Check if incognito windows (or normal windows) are disabled by policy.
   IncognitoModePrefs::Availability incognito_availability =
       profile_ ? IncognitoModePrefs::GetAvailability(profile_->GetPrefs())
                : IncognitoModePrefs::ENABLED;
 
-  BrowserThread::PostTask(
+  // Post the JumpListIcons update request with a brief delay.
+  BrowserThread::PostDelayedTask(
       BrowserThread::FILE, FROM_HERE,
       base::Bind(&JumpList::RunUpdateOnFileThread,
                  this,
-                 incognito_availability));
+                 incognito_availability),
+                 base::TimeDelta::FromMilliseconds(kDelayMSForJumplistUpdate));
+
+  {
+    // Record the request time (after posting the task) to allow filtering
+    // out redundant update requests.
+    base::AutoLock auto_lock(list_lock_);
+    lastUpdateRequested_ = base::TimeTicks::NowFromSystemTraceTime();
+  }
 }
 
 void JumpList::RunUpdateOnFileThread(
     IncognitoModePrefs::Availability incognito_availability) {
   ShellLinkItemList local_most_visited_pages;
   ShellLinkItemList local_recently_closed_pages;
 
   {
     base::AutoLock auto_lock(list_lock_);
     // Make sure we are not out of date: if icon_urls_ is not empty, then
     // another notification has been received since we processed this one
     if (!icon_urls_.empty())
       return;
 
+    // If we get a storm of update requests then we can skip most of the
+    // updates. Any update that starts after the last request will have
+    // done all the necessary work. This addresses this scenario:
+    // t=10.0: PostRunUpdate
+    // t=10.1: PostRunUpdate
+    // t=10.5: RunUpdateOnFileThread
+    // t=10.6: RunUpdateOnFileThread -- no update necessary!
+    // If the times are equal the meaning is ambiguous, so only return if
+    // the update-start time is clearly greater.
+    if (lastUpdateStarted_ > lastUpdateRequested_)
+      return;
+    lastUpdateStarted_ = base::TimeTicks::NowFromSystemTraceTime();
+
     // Make local copies of lists so we can release the lock.
     local_most_visited_pages = most_visited_pages_;
     local_recently_closed_pages = recently_closed_pages_;
   }
 
   // Delete the directory which contains old icon files, rename the current
   // icon directory, and create a new directory which contains new JumpList
   // icon files.
   base::FilePath icon_dir_old(icon_dir_.value() + L"Old");
   if (base::PathExists(icon_dir_old))
@@ skipping 28 matching lines @@
 
 void JumpList::TopSitesLoaded(history::TopSites* top_sites) {
 }
 
 void JumpList::TopSitesChanged(history::TopSites* top_sites) {
   top_sites->GetMostVisitedURLs(
       base::Bind(&JumpList::OnMostVisitedURLsAvailable,
                  weak_ptr_factory_.GetWeakPtr()),
       false);
 }