/usr/include/mirplatform/ is in libmirserver-dev 0.1.8+14.04.20140411-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/mirplatform/mir/
/usr/include/mirplatform/mir/abnormal_exit.h
/usr/include/mirplatform/mir/graphics/
/usr/include/mirplatform/mir/graphics/basic_platform.h
/usr/include/mirplatform/mir/graphics/buffer.h
/usr/include/mirplatform/mir/graphics/buffer_basic.h
/usr/include/mirplatform/mir/graphics/buffer_id.h
/usr/include/mirplatform/mir/graphics/buffer_initializer.h
/usr/include/mirplatform/mir/graphics/buffer_ipc_packer.h
/usr/include/mirplatform/mir/graphics/buffer_properties.h
/usr/include/mirplatform/mir/graphics/cursor.h
/usr/include/mirplatform/mir/graphics/display.h
/usr/include/mirplatform/mir/graphics/display_buffer.h
/usr/include/mirplatform/mir/graphics/display_configuration.h
/usr/include/mirplatform/mir/graphics/display_configuration_policy.h
/usr/include/mirplatform/mir/graphics/display_report.h
/usr/include/mirplatform/mir/graphics/drm_authenticator.h
/usr/include/mirplatform/mir/graphics/egl_extensions.h
/usr/include/mirplatform/mir/graphics/egl_resources.h
/usr/include/mirplatform/mir/graphics/event_handler_register.h
/usr/include/mirplatform/mir/graphics/gl_config.h
/usr/include/mirplatform/mir/graphics/gl_context.h
/usr/include/mirplatform/mir/graphics/graphic_buffer_allocator.h
/usr/include/mirplatform/mir/graphics/internal_client.h
/usr/include/mirplatform/mir/graphics/internal_surface.h
/usr/include/mirplatform/mir/graphics/native_platform.h
/usr/include/mirplatform/mir/graphics/nested_context.h
/usr/include/mirplatform/mir/graphics/overlapping_output_grouping.h
/usr/include/mirplatform/mir/graphics/pixel_format_utils.h
/usr/include/mirplatform/mir/graphics/platform.h
/usr/include/mirplatform/mir/graphics/platform_ipc_package.h
/usr/include/mirplatform/mir/graphics/renderable.h
/usr/include/mirplatform/mir/options/
/usr/include/mirplatform/mir/options/configuration.h
/usr/include/mirplatform/mir/options/default_configuration.h
/usr/include/mirplatform/mir/options/option.h
/usr/include/mirplatform/mir/options/program_option.h
/usr/include/mirplatform/mir/shared_library_loader.h
/usr/include/mirplatform/mir/udev/
/usr/include/mirplatform/mir/udev/wrapper.h