bug #74726: sr=waterson, r=beard. Make |nsXPIDLC?String| inherit from |nsSharableC?String|, the new implementation is now in the string hierarchy (and out of string/obsolete). This change to MozillaBuildFlags.txt makes it possible for Mac builds to selectively turn on string debugging and statistics machinery.

build/mac/build_scripts/MozillaBuildFlags.txt

@@ -67,6 +67,9 @@ xml_rpc         1
 cview           1
 help            1
 
+string_debug    0      DEBUG_STRING
+string_stats    0      DEBUG_STRING_STATS
+
 filepath_flags
 idepath             ":CodeWarrior IDE Path.txt"
 sessionpath         ":Mozilla session path.txt"