Tweaks to improve memory consumption by TopSites. The biggest culprit

chrome/browser/history/top_sites_cache.cc

 // Copyright (c) 2010 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/history/top_sites_cache.h"
 
 #include "base/logging.h"
 #include "base/ref_counted_memory.h"
 
 namespace history {
@@ skipping 30 matching lines @@
   std::map<GURL, Images>::const_iterator found =
       images_.find(GetCanonicalURL(url));
   if (found != images_.end()) {
     *bytes = found->second.thumbnail.get();
     return true;
   }
   return false;
 }
 
 GURL TopSitesCache::GetCanonicalURL(const GURL& url) {
-  std::map<GURL, size_t>::const_iterator i = canonical_urls_.find(url);
-  return i == canonical_urls_.end() ? url : top_sites_[i->second].url;
+  CanonicalURLs::iterator i = TopSitesCache::GetCanonicalURLsIterator(url);
+  return i == canonical_urls_.end() ? url : i->first.first->url;
 }
 
 bool TopSitesCache::IsKnownURL(const GURL& url) {
-  return canonical_urls_.find(url) != canonical_urls_.end();
+  return GetCanonicalURLsIterator(url) != canonical_urls_.end();
 }
 
 size_t TopSitesCache::GetURLIndex(const GURL& url) {
   DCHECK(IsKnownURL(url));
-  return canonical_urls_[url];
+  return GetCanonicalURLsIterator(url)->second;
 }
 
 void TopSitesCache::RemoveUnreferencedThumbnails() {
   for (URLToImagesMap::iterator i = images_.begin(); i != images_.end(); ) {
     if (IsKnownURL(i->first)) {
       ++i;
     } else {
       URLToImagesMap::iterator next_i = i;
       ++next_i;
       images_.erase(i);
       i = next_i;
     }
   }
 }
 
 void TopSitesCache::GenerateCanonicalURLs() {
   canonical_urls_.clear();
   for (size_t i = 0; i < top_sites_.size(); i++)
     StoreRedirectChain(top_sites_[i].redirects, i);
 }
 
 void TopSitesCache::StoreRedirectChain(const RedirectList& redirects,
                                        size_t destination) {
   // redirects is empty if the user pinned a site and there are not enough top
   // sites before the pinned site.
 
   // Map all the redirected URLs to the destination.
   for (size_t i = 0; i < redirects.size(); i++) {
     // If this redirect is already known, don't replace it with a new one.
-    if (canonical_urls_.find(redirects[i]) == canonical_urls_.end())
-      canonical_urls_[redirects[i]] = destination;
+    if (!IsKnownURL(redirects[i])) {
+      CanonicalURLEntry entry;
+      entry.first = &(top_sites_[destination]);
+      entry.second = i;
+      canonical_urls_[entry] = destination;
+    }
   }
 }
 
+TopSitesCache::CanonicalURLs::iterator TopSitesCache::GetCanonicalURLsIterator(
+    const GURL& url) {
+  MostVisitedURL most_visited_url;
+  most_visited_url.redirects.push_back(url);
+  CanonicalURLEntry entry;
+  entry.first = &most_visited_url;
+  entry.second = 0u;
+  return canonical_urls_.find(entry);
+}
+
 }  // namespace history