First version of the time slicing on the urls. Not ready for review yet.

chrome/browser/history/history_backend.cc

Index: chrome/browser/history/history_backend.cc
diff --git a/chrome/browser/history/history_backend.cc b/chrome/browser/history/history_backend.cc
index 2915f141be09a7d764099c19a4abf84708a15b6d..47c889c4a4e465527f8d3a3db67b0dbbee946aa4 100644
--- a/chrome/browser/history/history_backend.cc
+++ b/chrome/browser/history/history_backend.cc
@@ -25,6 +25,7 @@
 #include "chrome/browser/history/history_publisher.h"
 #include "chrome/browser/history/in_memory_history_backend.h"
 #include "chrome/browser/history/page_usage_data.h"
+#include "chrome/browser/history/time_filter.h"
 #include "chrome/browser/history/top_sites.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_notification_types.h"
@@ -1410,6 +1411,76 @@ void HistoryBackend::QueryMostVisitedURLs(
   request->ForwardResult(request->handle(), *result);
 }
 
+void HistoryBackend::QueryMostVisitedURLsDuringTime(
+      scoped_refptr<QueryMostVisitedURLsRequest> request,
+      int result_count,
+      const history::TimeFilter& filter)  {
+  if (request->canceled())
+    return;
+
+  if (!db_.get()) {
+    // No History Database - return an empty list.
+    request->ForwardResult(request->handle(), MostVisitedURLList());
+    return;
+  }
+
+  VisitVector visits;
+  db_->GetVisibleVisitsDuringTimes(filter, 0, &visits);
+
+  std::map<URLID, double> score_map;
+  const double kLn2 = 0.6931471805599453;
+  base::Time now = base::Time::Now();
+  for (size_t i = 0; i < visits.size(); ++i) {
+    // Decay score by half each week.
+    base::TimeDelta time_passed = now - visits[i].visit_time;
+    // Clamp to 0 in case time jumps backwards (e.g. due to DST).
+    double decay_exponent = std::max(0.0, kLn2 * static_cast<double>(
+        time_passed.InMicroseconds()) / base::Time::kMicrosecondsPerWeek);
+    double score = 1.0 / exp(decay_exponent);
+    std::map<URLID, double>::iterator it = score_map.find(visits[i].url_id);
+    if (it == score_map.end())
+      score_map[visits[i].url_id] = score;
+    else
+      it->second += score;
+  }
+
+  ScopedVector<PageUsageData> data;
+  data->reserve(score_map.size());
+  for (std::map<URLID, double>::iterator it = score_map.begin();
+       it != score_map.end(); ++it) {
+    PageUsageData *one_url = new PageUsageData(it->first);
+    one_url->SetScore(it->second);
+    data->push_back(one_url);
+  }
+
+  // Limit to the top |result_count| results.
+  std::sort(data.begin(), data.end(), PageUsageData::Predicate);
+  if (result_count && static_cast<int>(data.size()) > result_count) {
+    STLDeleteContainerPointers(data.begin() + result_count, data.end());
+    data.resize(result_count);
+  }
+
+  for (size_t i = 0; i < data->size(); ++i) {
+    PageUsageData* pud = data[i];
+    URLRow info;
+    if (db_->GetURLRow(pud->GetID(), &info)) {
+      pud->SetURL(info.url());
+      pud->SetTitle(info.title());
+    }
+  }
+
+  MostVisitedURLList& result = request->value;
+  for (size_t i = 0; i < data.size(); ++i) {
+    PageUsageData* current_data = data[i];
+    RedirectList redirects;
+    GetMostRecentRedirectsFrom(current_data->GetURL(), &redirects);
+    MostVisitedURL url = MakeMostVisitedURL(*current_data, redirects);
+    result.push_back(url);
+  }
+
+  request->ForwardResult(request->handle(), result);
+}
+
 void HistoryBackend::QueryMostVisitedURLsImpl(int result_count,
                                               int days_back,
                                               MostVisitedURLList* result) {