Rewrite the Android implementation of BatteryMonitor directly in Java.

device/battery/battery_status_manager_android.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 "device/battery/battery_status_manager_android.h"
-
-#include "base/android/jni_android.h"
-#include "base/android/scoped_java_ref.h"
-#include "base/metrics/histogram.h"
-#include "jni/BatteryStatusManager_jni.h"
-
-using base::android::AttachCurrentThread;
-
-namespace device {
-
-BatteryStatusManagerAndroid::BatteryStatusManagerAndroid(
-    const BatteryStatusService::BatteryUpdateCallback& callback)
-    : callback_(callback) {
-  j_manager_.Reset(
-      Java_BatteryStatusManager_getInstance(
-          AttachCurrentThread(), base::android::GetApplicationContext()));
-}
-
-BatteryStatusManagerAndroid::~BatteryStatusManagerAndroid() {
-}
-
-// static
-bool BatteryStatusManagerAndroid::Register(JNIEnv* env) {
-  return RegisterNativesImpl(env);
-}
-
-void BatteryStatusManagerAndroid::GotBatteryStatus(JNIEnv*,
-                                                   jobject,
-                                                   jboolean charging,
-                                                   jdouble charging_time,
-                                                   jdouble discharging_time,
-                                                   jdouble level) {
-  BatteryStatus status;
-  status.charging = charging;
-  status.charging_time = charging_time;
-  status.discharging_time = discharging_time;
-  status.level = level;
-  callback_.Run(status);
-}
-
-bool BatteryStatusManagerAndroid::StartListeningBatteryChange() {
-  bool result = Java_BatteryStatusManager_start(AttachCurrentThread(),
-      j_manager_.obj(), reinterpret_cast<intptr_t>(this));
-  UMA_HISTOGRAM_BOOLEAN("BatteryStatus.StartAndroid", result);

[timvolodine, 2014/12/15 12:47:21]

any chance we could keep UMA logging with the new approach? I looks like you are
dropping support for this in the patch.

[ppi, 2014/12/15 13:52:37]

Good catch, thanks!

The way UMA works now (with no real Java support), adding the call to
UMA_HISTOGRAM_BOOLEAN would unfortunately undo much of the benefits of this
change - the implementation would not be pure Java and we would need to bring
the JNI back.

Given that this particular histogram seems to be recording 100.00% of successes
for the last one month, I wonder if we should replace it with an assert on the
Java side in the new implementation, as a provisional measure until we get
resolution on http://crbug.com/442300 .

Wdyt?

-  return result;
-}
-
-void BatteryStatusManagerAndroid::StopListeningBatteryChange() {
-  Java_BatteryStatusManager_stop(
-      AttachCurrentThread(), j_manager_.obj());
-}
-
-// static
-scoped_ptr<BatteryStatusManager> BatteryStatusManager::Create(
-    const BatteryStatusService::BatteryUpdateCallback& callback) {
-  return scoped_ptr<BatteryStatusManager>(
-      new BatteryStatusManagerAndroid(callback));
-}
-
-}  // namespace device