Add support to Battery Status API in blink.

Source/modules/modules.gypi

 {
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
     # ways.
     'extra_blink_module_idl_files': [],
     'extra_blink_module_files': [],
     # Files for which bindings (.cpp and .h files) will be generated
     'modules_idl_files': [
       '<@(extra_blink_module_idl_files)',
+      'battery/BatteryManager.idl',
       'crypto/AesKeyAlgorithm.idl',
       'crypto/Crypto.idl',
       'crypto/HmacKeyAlgorithm.idl',
       'crypto/Key.idl',
       'crypto/KeyAlgorithm.idl',
       'crypto/KeyPair.idl',
       'crypto/RsaHashedKeyAlgorithm.idl',
       'crypto/RsaKeyAlgorithm.idl',
       'crypto/SubtleCrypto.idl',
       'crypto/WorkerCrypto.idl',
@@ skipping 155 matching lines @@
       'webmidi/MIDIInput.idl',
       'webmidi/MIDIMessageEvent.idl',
       'webmidi/MIDIOutput.idl',
       'webmidi/MIDIPort.idl',
       'webmidi/MIDISuccessCallback.idl',
       'websockets/CloseEvent.idl',
       'websockets/WebSocket.idl',
     ],
     # 'partial interface' or target (right side of) 'implements'
     'modules_dependency_idl_files': [
+      'battery/NavigatorBattery.idl',
       'crypto/WindowCrypto.idl',
       'crypto/WorkerGlobalScopeCrypto.idl',
       'donottrack/NavigatorDoNotTrack.idl',
       'filesystem/DataTransferItemFileSystem.idl',
       'filesystem/HTMLInputElementFileSystem.idl',
       'filesystem/InspectorFrontendHostFileSystem.idl',
       'filesystem/WindowFileSystem.idl',
       'filesystem/WorkerGlobalScopeFileSystem.idl',
       'gamepad/NavigatorGamepad.idl',
       'geolocation/NavigatorGeolocation.idl',
@@ skipping 17 matching lines @@
       'screen_orientation/ScreenOrientation.idl',
       'serviceworkers/NavigatorServiceWorker.idl',
       'speech/WindowSpeechSynthesis.idl',
       'vibration/NavigatorVibration.idl',
       'webdatabase/WindowWebDatabase.idl',
       'webdatabase/WorkerGlobalScopeWebDatabase.idl',
       'webmidi/NavigatorWebMIDI.idl',
     ],
     'modules_files': [
       '<@(extra_blink_module_files)',
+      'battery/BatteryManager.cpp',
+      'battery/BatteryManager.h',
+      'battery/BatteryStatus.cpp',
+      'battery/BatteryStatus.h',
+      'battery/NavigatorBattery.cpp',
+      'battery/NavigatorBattery.h',
       'crypto/Crypto.cpp',
       'crypto/Crypto.h',
       'crypto/CryptoResultImpl.cpp',
       'crypto/CryptoResultImpl.h',
       'crypto/DOMWindowCrypto.cpp',
       'crypto/DOMWindowCrypto.h',
       'crypto/Key.cpp',
       'crypto/AesKeyAlgorithm.cpp',
       'crypto/AesKeyAlgorithm.h',
       'crypto/HmacKeyAlgorithm.cpp',
@@ skipping 633 matching lines @@
       'indexeddb/IDBKeyPathTest.cpp',
       'indexeddb/IDBRequestTest.cpp',
       'indexeddb/IDBTransactionTest.cpp',
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }