Cancel the JumpList update if top 5 most visited URLs are unchanged

chrome/browser/win/jumplist.cc

Index: chrome/browser/win/jumplist.cc
diff --git a/chrome/browser/win/jumplist.cc b/chrome/browser/win/jumplist.cc
index 7f8ecf1257bda62023d10ea3bf2b181b72fe7a6c..33cf249633debfaaefc272506d95e2ccb1291a34 100644
--- a/chrome/browser/win/jumplist.cc
+++ b/chrome/browser/win/jumplist.cc
@@ -4,6 +4,9 @@
 
 #include "chrome/browser/win/jumplist.h"
 
+#include <algorithm>
+#include <iterator>
+
 #include "base/base_paths.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ -193,6 +196,25 @@ base::FilePath GenerateJumplistIconDirName(
   return profile_dir.Append(dir_name);
 }
 
+// Checks if the urls stored in |items| have new ones coming from |urls|.
+bool HasNewMostVisitedItems(const ShellLinkItemList& items,
+                            const history::MostVisitedURLList& urls) {
+  // If the number of the top sites going to be displayed is larger than the
+  // current one, or if the available urls from TopSites are fewer than the ones
+  // currenlty in display, we consider there are new most visited items.
+  // Otherwise, check if the current urls stored in |items| are different from
+  // |urls| to determine if there are new items.
+
+  size_t topsites_count_updated = std::min(urls.size(), kMostVisitedItems);
+  if (topsites_count_updated > items.size() || urls.size() < items.size())
+    return true;
+
+  return std::equal(std::begin(items), std::end(items), std::begin(urls),

[grt (UTC plus 2), 2017/05/29 07:14:44]

shouldn't this return false if the ranges are equal since that indicates that
the top N urls haven't changed?

[chengx, 2017/05/30 02:56:44]

You're right. I've fixed this in the new patch set.

+                    [](const auto& item_ptr, const auto& most_visited_url) {
+                      return item_ptr->url() == most_visited_url.url.spec();
+                    });
+}
+
 }  // namespace
 
 JumpList::JumpListData::JumpListData() {}
@@ -292,6 +314,12 @@ void JumpList::OnMostVisitedURLsAvailable(
   {
     JumpListData* data = &jumplist_data_->data;
     base::AutoLock auto_lock(data->list_lock_);
+
+    // There is no need to update the JumpList if the top most visited sites in
+    // display have not changed.
+    if (!HasNewMostVisitedItems(data->most_visited_pages_, urls))
+      return;
+
     data->most_visited_pages_.clear();
 
     for (size_t i = 0; i < urls.size() && i < kMostVisitedItems; i++) {