gl-renderer: Add support for fence sync extensions

Check for the EGL_KHR_fence_sync and EGL_ANDROID_native_fence_sync
extensions and get pointers to required extension functions.

These extensions allow us to acquire GPU timestamp information
asynchronously, and are required by the upcoming work to add
rendering begin/end timepoints to the weston timeline.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/libweston/gl-renderer.c b/libweston/gl-renderer.c
index 5768f05..c2e88a6 100644
--- a/libweston/gl-renderer.c
+++ b/libweston/gl-renderer.c
@@ -231,6 +231,11 @@
 	int has_dmabuf_import_modifiers;
 	PFNEGLQUERYDMABUFFORMATSEXTPROC query_dmabuf_formats;
 	PFNEGLQUERYDMABUFMODIFIERSEXTPROC query_dmabuf_modifiers;
+
+	int has_native_fence_sync;
+	PFNEGLCREATESYNCKHRPROC create_sync;
+	PFNEGLDESTROYSYNCKHRPROC destroy_sync;
+	PFNEGLDUPNATIVEFENCEFDANDROIDPROC dup_native_fence_fd;
 };
 
 static PFNEGLGETPLATFORMDISPLAYEXTPROC get_platform_display = NULL;
@@ -3028,6 +3033,17 @@
 	if (weston_check_egl_extension(extensions, "GL_EXT_texture_rg"))
 		gr->has_gl_texture_rg = 1;
 
+	if (weston_check_egl_extension(extensions, "EGL_KHR_fence_sync") &&
+	    weston_check_egl_extension(extensions, "EGL_ANDROID_native_fence_sync")) {
+		gr->create_sync =
+			(void *) eglGetProcAddress("eglCreateSyncKHR");
+		gr->destroy_sync =
+			(void *) eglGetProcAddress("eglDestroySyncKHR");
+		gr->dup_native_fence_fd =
+			(void *) eglGetProcAddress("eglDupNativeFenceFDANDROID");
+		gr->has_native_fence_sync = 1;
+	}
+
 	renderer_setup_egl_client_extensions(gr);
 
 	return 0;