gtk: refactor copy-pasted code

gfx/gtk_util.h

Index: gfx/gtk_util.h
diff --git a/gfx/gtk_util.h b/gfx/gtk_util.h
index 5c4ad94bfd342a5495faa506fce010178d58c397..8f9618dd9797079514532cf4bc7e1d84f7b7ddcb 100644
--- a/gfx/gtk_util.h
+++ b/gfx/gtk_util.h
@@ -17,12 +17,18 @@
 typedef struct _GdkPixbuf GdkPixbuf;
 typedef struct _GdkRegion GdkRegion;
 
+class CommandLine;
 class SkBitmap;
 
 namespace gfx {
 
 class Rect;
 
+// Call gtk_init() using the argc and argv from command_line.
+// gtk_init() wants an argc and argv that it can mutate; we provide those,
+// but leave the original CommandLine unaltered.
+void GtkInitFromCommandLine(const CommandLine& command_line);
+
 // Convert and copy a SkBitmap to a GdkPixbuf. NOTE: this uses BGRAToRGBA, so
 // it is an expensive operation.  The returned GdkPixbuf will have a refcount of
 // 1, and the caller is responsible for unrefing it when done.