Expose cellular signal strength on Android to native

net/android/cellular_signal_strength.cc

Index: net/android/cellular_signal_strength.cc
diff --git a/net/android/cellular_signal_strength.cc b/net/android/cellular_signal_strength.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b0d07fb6bffa42be403d44ee3ad4679fc4e60ccf
--- /dev/null
+++ b/net/android/cellular_signal_strength.cc
@@ -0,0 +1,58 @@
+// Copyright 2016 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 "net/android/cellular_signal_strength.h"
+
+#include <stdint.h>
+
+#include "base/android/context_utils.h"
+#include "jni/AndroidCellularSignalStrength_jni.h"
+
+namespace net {
+
+namespace android {
+
+namespace cellular_signal_strength {
+
+// GENERATED_JAVA_ENUM_PACKAGE: org.chromium.net
+enum CellularSignalStrengthError {
+  // Value returned by CellularSignalStrength APIs when a valid value is
+  // unavailable.
+  ERROR_NOT_SUPPORTED = -2147483647 - 1,

[pauljensen, 2016/05/23 12:25:10]

why the subtraction?

[tbansal1, 2016/06/09 17:50:30]

This is INT32_MIN. I just set it directly to  -2147483648.

+};
+
+bool GetRssiDbm(int* rssi) {
+  static_assert(
+      INT32_MIN == ERROR_NOT_SUPPORTED,
+      "CellularSignalStrengthError.ERROR_NOT_SUPPORTED has unexpected value");

[pauljensen, 2016/05/23 12:25:10]

can we move this assert up a scope level to right below ERROR_NOT_SUPPORTED's
definition?

[tbansal1, 2016/06/09 17:50:30]

Done.

+  int rssi_tmp = Java_AndroidCellularSignalStrength_getRssiDbm(
+      base::android::AttachCurrentThread(),
+      base::android::GetApplicationContext());
+  if (rssi_tmp == ERROR_NOT_SUPPORTED)
+    return false;
+
+  *rssi = rssi_tmp;
+  return true;
+}
+
+bool GetSignalLevel(int* signal_level) {
+  int signal_level_tmp = Java_AndroidCellularSignalStrength_getSignalLevel(
+      base::android::AttachCurrentThread(),
+      base::android::GetApplicationContext());
+  if (signal_level_tmp == ERROR_NOT_SUPPORTED)
+    return false;
+
+  *signal_level = signal_level_tmp;
+  return true;
+}
+
+bool Register(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+}  // namespace cellular_signal_strength
+
+}  // namespace android
+
+}  // namespace net