b=467874 only destroy FT_Faces created by cairo. r=vlad

gfx/cairo/README

@@ -36,6 +36,8 @@ qpainter-type.patch: add SURFACE_TYPE_QPAINTER to cairo.h
 
 wince-fixes.patch: stubs out win32 functions we use but are not supported on win32.  Also implements ExtSelectClipRgn in terms of other functions available on wince.
 
+ft-done-face.patch: bug 467874; only destroy FT_Faces created by cairo
+
 ==== pixman patches ====
 
 endian.patch: include cairo-platform.h for endian macros

gfx/cairo/cairo/src/cairo-ft-font.c

@@ -532,7 +532,8 @@ _has_unlocked_face (void *entry)
 {
     cairo_ft_unscaled_font_t *unscaled = entry;
 
-    return (unscaled->lock_count == 0 && unscaled->face);
+    return (unscaled->lock_count == 0 &&
+	    unscaled->face && !unscaled->from_face);
 }
 
 /* Ensures that an unscaled font has a face object. If we exceed

gfx/cairo/ft-done-face.patch

@@ -0,0 +1,13 @@
+diff --git a/gfx/cairo/cairo/src/cairo-ft-font.c b/gfx/cairo/cairo/src/cairo-ft-font.c
+--- a/gfx/cairo/cairo/src/cairo-ft-font.c
++++ b/gfx/cairo/cairo/src/cairo-ft-font.c
+@@ -532,7 +532,8 @@ _has_unlocked_face (void *entry)
+ {
+     cairo_ft_unscaled_font_t *unscaled = entry;
+ 
+-    return (unscaled->lock_count == 0 && unscaled->face);
++    return (unscaled->lock_count == 0 &&
++	    unscaled->face && !unscaled->from_face);
+ }
+ 
+ /* Ensures that an unscaled font has a face object. If we exceed