Reland: Add a public cpp targets for devices_app

This exposes the bare minimum stuff necessary to build a devices
app delegate, hiding the impl details behind a private
dependency.

Reland corrects a missing include in the app's main.cc.

This is a reland of the reland! The reland was reverted due
to suspicion of cast_shell_linux breakage, but that was
caused by something else.

BUG=None
TBR=reillyg@chromium.org,sky@chromium.org

Review URL: https://codereview.chromium.org/1213613018

Cr-Commit-Position: refs/heads/master@{#337725}

1 files changed, 2 insertions, 11 deletions

diff --git a/device/devices_app/devices_app.h b/device/devices_app/devices_app.h
index 4b04568..eda8d4c 100644
--- a/device/devices_app/devices_app.h
+++ b/device/devices_app/devices_app.h
@@ -27,26 +27,17 @@ namespace usb {
 class DeviceManager;
 }
 
-extern const char kDevicesMojoAppUrl[];
-
 class DevicesApp : public mojo::ApplicationDelegate,
                    public mojo::InterfaceFactory<usb::DeviceManager>,
                    public mojo::ErrorHandler {
  public:
-  ~DevicesApp() override;
-
-  // |service_task_runner| is the thread TaskRunner on which the UsbService
-  // lives. This argument should be removed once UsbService is owned by the
-  // USB device manager and no longer part of the public device API. If null,
-  // the app will construct its own DeviceClient and UsbService.
-  static scoped_ptr<mojo::ApplicationDelegate> CreateDelegate(
+  explicit DevicesApp(
       scoped_refptr<base::SequencedTaskRunner> service_task_runner);
+  ~DevicesApp() override;
 
  private:
   class USBServiceInitializer;
 
-  DevicesApp(scoped_refptr<base::SequencedTaskRunner> service_task_runner);
-
   // mojo::ApplicationDelegate:
   void Initialize(mojo::ApplicationImpl* app) override;
   bool ConfigureIncomingConnection(