This is key to both reducing bloat, and to solving the need for NULL strings in the DOM (see bug # 6052). This does _not_ mean we need to replace |ns[C]String| with the copy-on-write implementation this close to release; but we do these classes in the tree.

Now that string has been split into its own library, this has become bug #1 for me. Several other bugs depend on this bug. Attaching dependencies now.

modified summary to vet the name I want to use

|nsCommon[C]String| must also support the usage patterns of |nsXPIDL[C]String| (see bug #)16108, adding the capability of re-binding (e.g., the intent of bug #40140: |getter_InOut|. Merging those two bugs into this one closing them as dups.

*** Bug 16108 has been marked as a duplicate of this bug. ***

*** Bug 40140 has been marked as a duplicate of this bug. ***

(mass change) didn't get these in for target milestone mozilla0.8.1 but they are very close. Moving all to mozilla0.9.

Landed the branch; this class now exists and, in fact, is used to implement |nsPromiseFlat[C]String|. There's still more work to do here. Need to make this a writable string and add xpidl-string functionality. Filed bug #74726 for that purpose. Marking this bug fixed.