Add a built-in screencast recording facility

For development and demonstration purposes, it's neat to be able to
record a screencast of gnome-shell without any external setup.
Built-in recording can also give much better quality than is possible
with a generic desktop recording, since we hook right into the paint
loop.

src/shell-recorder.[ch]: A general-purposes object to record a Clutter
 stage to a GStreamer stream.
src/shell-recorder-src.[ch]: A simple GStreamer source element (similar
 to appsrc in the most recent versions of GStreamer) for injecting
 captured data into a GStreamer pipeline.
src/test-recorder.c: Test program that records a simple animation.

configure.ac src/Makefile.am: Add machinery to conditionally build
 ShellRecorder.
tools/build/gnome-shell-build-setup.sh: Add gstreamer packages
 to the list of required packages for Fedora.

js/ui/main.js: Hook up the recorder to a MetaScreen ::toggle-recording
 keybinding.

http://bugzilla.gnome.org/show_bug.cgi?id=575290

src/shell-recorder-src.h

@@ -0,0 +1,39 @@
+#ifndef __SHELL_RECORDER_SRC_H__
+#define __SHELL_RECORDER_SRC_H__
+
+#include <gst/gst.h>
+
+G_BEGIN_DECLS
+
+/**
+ * ShellRecorderSrc:
+ *
+ * shellrecordersrc a custom source element is pretty much like a very
+ * simple version of the stander GStreamer 'appsrc' element, without
+ * any of the provisions for seeking, generating data on demand,
+ * etc. In both cases, the application supplies the buffers and the
+ * element pushes them into the pipeline. The main reason for not using
+ * appsrc is that it wasn't a supported element until gstreamer 0.10.22,
+ * and as of 2009-03, many systems still have 0.10.21.
+ */
+typedef struct _ShellRecorderSrc      ShellRecorderSrc;
+typedef struct _ShellRecorderSrcClass ShellRecorderSrcClass;
+
+#define SHELL_TYPE_RECORDER_SRC              (shell_recorder_src_get_type ())
+#define SHELL_RECORDER_SRC(object)           (G_TYPE_CHECK_INSTANCE_CAST ((object), SHELL_TYPE_RECORDER_SRC, ShellRecorderSrc))
+#define SHELL_RECORDER_SRC_CLASS(klass)      (G_TYPE_CHECK_CLASS_CAST ((klass), SHELL_TYPE_RECORDER_SRC, ShellRecorderSrcClass))
+#define SHELL_IS_RECORDER_SRC(object)        (G_TYPE_CHECK_INSTANCE_TYPE ((object), SHELL_TYPE_RECORDER_SRC))
+#define SHELL_IS_RECORDER_SRC_CLASS(klass)   (G_TYPE_CHECK_CLASS_TYPE ((klass), SHELL_TYPE_RECORDER_SRC))
+#define SHELL_RECORDER_SRC_GET_CLASS(obj)    (G_TYPE_INSTANCE_GET_CLASS ((obj), SHELL_TYPE_RECORDER_SRC, ShellRecorderSrcClass))
+
+GType              shell_recorder_src_get_type     (void) G_GNUC_CONST;
+
+void shell_recorder_src_register (void);
+
+void shell_recorder_src_add_buffer (ShellRecorderSrc *src,
+				    GstBuffer        *buffer);
+void shell_recorder_src_close      (ShellRecorderSrc *src);
+
+G_END_DECLS
+
+#endif /* __SHELL_RECORDER_SRC_H__ */