Bug 893222 - Part 0: Make JSRope::getCharsNonDestructiveInternal work with a null tcx.
Bug 893222 - Part 1: Add a new PutEscapedString implementation, which takes a raw jschar*.
Bug 893222 - Part 2: Modify the JS memory reporter to consider a string as "notable" if we have many small copies of it.
Bug 893222 - Part 3: Rework JS memory reporters so gc-heap is no longer a top-level node.