[Device Service] Move Gamepad Blink headers to be part of the Gamepad client library

ppapi/shared_impl/ppb_gamepad_shared.h

Index: ppapi/shared_impl/ppb_gamepad_shared.h
diff --git a/ppapi/shared_impl/ppb_gamepad_shared.h b/ppapi/shared_impl/ppb_gamepad_shared.h
index df95fab8340a0e617ccdf4a4ed75dc537451f492..24f3cb0dc73887f34c4dfe21b58257329f5a6d6d 100644
--- a/ppapi/shared_impl/ppb_gamepad_shared.h
+++ b/ppapi/shared_impl/ppb_gamepad_shared.h
@@ -12,6 +12,10 @@
 #include "ppapi/c/ppb_gamepad.h"
 #include "ppapi/shared_impl/ppapi_shared_export.h"
 
+namespace device {
+class Gamepads;
+}
+
 namespace ppapi {
 
 // TODO(brettw) when we remove the non-IPC-based gamepad implementation, this
@@ -119,6 +123,10 @@ PPAPI_SHARED_EXPORT void ConvertWebKitGamepadData(
     const WebKitGamepads& webkit_data,
     PP_GamepadsSampleData* output_data);
 
+PPAPI_SHARED_EXPORT void ConvertDeviceGamepadData(
+    const device::Gamepads& device_data,
+    PP_GamepadsSampleData* output_data);
+
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_PPB_GAMEPAD_SHARED_H_