battery-status: Implement the battery-status API for chromeos.

content/browser/battery_status/battery_status_manager_chromeos.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 "content/browser/battery_status/battery_status_manager.h"
+
+#include "base/memory/weak_ptr.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/power_manager/power_supply_properties.pb.h"
+#include "chromeos/dbus/power_manager_client.h"
+#include "content/public/browser/browser_thread.h"
+#include "third_party/WebKit/public/platform/WebBatteryStatus.h"
+
+namespace content {
+
+namespace {
+
+class BatteryStatusManagerChromeOS
+    : public BatteryStatusManager,
+      public chromeos::PowerManagerClient::Observer {
+ public:
+  explicit BatteryStatusManagerChromeOS(
+      const BatteryStatusService::BatteryUpdateCallback& callback)
+      : callback_(callback), currently_listening_(false), weak_factory_(this) {
+  }
+
+  virtual ~BatteryStatusManagerChromeOS() {
+    StopOnUI();

[timvolodine, 2014/07/02 19:41:39]

nit: so the destructor should be called on the UI thread only? maybe mention
this in a comment..

I was actually wondering if there is an easy solution to make it destructable on
any thread, in case we would decide to clean-up the object when it's not needed
(and not only in BatteryStatusService::Shutdown()).

[sadrul, 2014/07/04 16:58:18]

I have changed this so the BatteryStatusManager object can be destroyed on any
thread.

+  }
+
+ private:
+  bool IsBatteryPresent(
+      const power_manager::PowerSupplyProperties& proto) const {
+    return proto.battery_state() !=
+           power_manager::PowerSupplyProperties_BatteryState_NOT_PRESENT;

[timvolodine, 2014/07/02 19:41:39]

nit: indent +4 spaces as in the method below. this seems to apply to
IsBatteryCharging and IsBatteryFull as well.

[sadrul, 2014/07/04 16:58:18]

This is how 'git cl format' formats it. Do you feel strongly that I should
change this to 4-space indent regardless?

[timvolodine, 2014/07/09 11:35:01]

I don't feel strongly about those indents as long as they are consistent, which
they are now :)

+  }
+
+  bool IsUsbChargerConnected(
+      const power_manager::PowerSupplyProperties& proto) const {
+    return proto.external_power() ==
+        power_manager::PowerSupplyProperties_ExternalPower_USB;
+  }
+
+  bool IsBatteryCharging(
+      const power_manager::PowerSupplyProperties& proto) const {
+    return proto.battery_state() !=
+           power_manager::PowerSupplyProperties_BatteryState_DISCHARGING;
+  }
+
+  bool IsBatteryFull(const power_manager::PowerSupplyProperties& proto) const {
+    return proto.battery_state() ==
+           power_manager::PowerSupplyProperties_BatteryState_FULL;
+  }
+
+  double GetBatteryLevel(
+      const power_manager::PowerSupplyProperties& proto) const {
+    const double kMaxBatteryLevelProto = 100.f;
+    return proto.battery_percent() / kMaxBatteryLevelProto;
+  }
+
+  void StartOnUI() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (!currently_listening_) {

[timvolodine, 2014/07/02 19:41:39]

nit: early return as in Stop?

[sadrul, 2014/07/04 16:58:18]

Done.

+      chromeos::DBusThreadManager::Get()->GetPowerManagerClient()->AddObserver(
+          this);
+      chromeos::DBusThreadManager::Get()
+          ->GetPowerManagerClient()
+          ->RequestStatusUpdate();
+    }
+    currently_listening_ = true;
+  }
+
+  void StopOnUI() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (!currently_listening_)
+      return;
+    chromeos::DBusThreadManager::Get()->GetPowerManagerClient()->RemoveObserver(
+        this);
+    currently_listening_ = false;
+  }
+
+  // BatteryStatusManager:
+  virtual bool StartListeningBatteryChange() OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+    weak_factory_.InvalidateWeakPtrs();
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                            base::Bind(&BatteryStatusManagerChromeOS::StartOnUI,
+                                       weak_factory_.GetWeakPtr()));
+    return true;
+  }
+
+  virtual void StopListeningBatteryChange() OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+    weak_factory_.InvalidateWeakPtrs();
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                            base::Bind(&BatteryStatusManagerChromeOS::StopOnUI,
+                                       weak_factory_.GetWeakPtr()));
+  }
+
+  // chromeos::PowerManagerClient::Observer:
+  virtual void PowerChanged(

[timvolodine, 2014/07/02 19:41:39]

just out of curiosity: is this usually called when level changes by 1percent on
chromeos?

[sadrul, 2014/07/04 16:58:18]

From a quick test: this can trigger more often than that, e.g. to update the
charging/discharging time (on average, it looks like there are two updates every
minute). This is the same notification used to update the battery indicator in
the system-tray on Chrome OS.

[timvolodine, 2014/07/09 11:35:01]

yeah, looks like this depends on device/system..

+      const power_manager::PowerSupplyProperties& proto) OVERRIDE {
+    blink::WebBatteryStatus status;
+    if (IsBatteryPresent(proto)) {
+      // The charging status is unreliable if a low power charger is connected
+      // (i.e. usb). So set |chargingTime| and |dischargingTime| only when usb
+      // charger is not connected.
+      if (!IsUsbChargerConnected(proto)) {
+        status.charging = IsBatteryCharging(proto);
+
+        // Do not set |chargingTime| and |dischargingTime| if the time is still

[timvolodine, 2014/07/02 19:41:39]

If the chargingTime cannot be provided (maybe temporarily) it should be set to
+infinity. This is different from the blink::WebBatteryStatus defaults because
they are designed to emulate a "full" battery.

We recently had some discussions regarding the default values on
public-device-apis@w3.org, the spec should be updated now to make it more clear
(https://dvcs.w3.org/hg/dap/raw-file/default/battery/Overview.html)

[sadrul, 2014/07/04 16:58:18]

Done.

+        // being computed (and not reliable).
+        if (!proto.is_calculating_battery_time()) {
+          // Set |chargingTime| if the battery is charging, and it isn't full.
+          if (status.charging && !IsBatteryFull(proto))
+            status.chargingTime = proto.battery_time_to_full_sec();
+
+          // Set |dischargingTime| if the battery is not charging.
+          if (!status.charging)
+            status.dischargingTime = proto.battery_time_to_empty_sec();
+        }
+      }
+
+      status.level = GetBatteryLevel(proto);
+    }
+    callback_.Run(status);
+  }
+
+  BatteryStatusService::BatteryUpdateCallback callback_;
+  bool currently_listening_;
+  base::WeakPtrFactory<BatteryStatusManagerChromeOS> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryStatusManagerChromeOS);
+};
+
+}  // namespace
+
+// static
+BatteryStatusManager* BatteryStatusManager::Create(
+    const BatteryStatusService::BatteryUpdateCallback& callback) {
+  return new BatteryStatusManagerChromeOS(callback);
+}
+
+}  // namespace content