[camera] Fix wrong orientation (#36)

* Fixed the bug. See: #6 (comment)

* Also, I changed the camera type from back-camera to external-camera.

packages/camera/elinux/camera_elinux_plugin.cc

@@ -208,7 +208,7 @@ void CameraPlugin::HandleAvailableCamerasCall(
     AvailableCamerasMessage camera;
     camera.SetName("camera" + std::to_string(i));
     camera.SetSensorOrientation(0);
-    camera.SetLensFacing("back");
+    camera.SetLensFacing("external");
     cameras.push_back(camera.ToMap());
   }
 

packages/camera/elinux/channels/method_channel_device.cc

@@ -9,7 +9,7 @@
 
 namespace {
 constexpr char kChannelName[] = "flutter.io/cameraPlugin/device";
-constexpr char kChannelMethodInitialized[] = "initialized";
+constexpr char kChannelMethodOrientationChanged[] = "orientation_changed";
 
 constexpr char kOrientation[] = "orientation";
 };  // namespace
@@ -27,7 +27,7 @@ void MethodChannelDevice::SendDeviceOrientationChangeEvent(
       flutter::EncodableValue(SerializeDeviceOrientation(orientation));
   auto value = std::make_unique<flutter::EncodableValue>(mp);
 
-  Send(kChannelMethodInitialized, std::move(value));
+  Send(kChannelMethodOrientationChanged, std::move(value));
 }
 
 void MethodChannelDevice::Send(