[chromeos] Limit the data samples stored by PowerDataCollector.

chrome/browser/ui/webui/chromeos/power_ui.cc

 // Copyright 2014 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/ui/webui/chromeos/power_ui.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/compiler_specific.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 36 matching lines @@
 }
 
 void PowerMessageHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       kRequestBatteryChargeDataCallback,
       base::Bind(&PowerMessageHandler::OnGetBatteryChargeData,
                  base::Unretained(this)));
 }
 
 void PowerMessageHandler::OnGetBatteryChargeData(const base::ListValue* value) {
-  const std::vector<PowerDataCollector::PowerSupplySnapshot>& power_supply =
+  const std::deque<PowerDataCollector::PowerSupplySnapshot>& power_supply =
       PowerDataCollector::Get()->power_supply_data();
   base::ListValue data;
 
   for (unsigned int i = 0; i < power_supply.size(); ++i) {
     const PowerDataCollector::PowerSupplySnapshot& snapshot = power_supply[i];
     base::Time time = base::Time::Now() -
-        (base::TimeTicks::Now() - power_supply[i].time);
+        (base::TimeTicks::Now() - snapshot.time);
     scoped_ptr<base::DictionaryValue> element(new base::DictionaryValue);
     element->SetDouble("battery_percent", snapshot.battery_percent);
     element->SetBoolean("external_power", snapshot.external_power);
     element->SetDouble("time", time.ToJsTime());
 
     data.Append(element.release());
   }
 
   web_ui()->CallJavascriptFunction(kOnRequestBatteryChargeDataFunction, data);
 }
@@ skipping 22 matching lines @@
   html->SetDefaultResource(IDR_ABOUT_POWER_HTML);
 
   Profile* profile = Profile::FromWebUI(web_ui);
   content::WebUIDataSource::Add(profile, html);
 }
 
 PowerUI::~PowerUI() {
 }
 
 }  // namespace chromeos