Merge pull request #14547 from davidflanagan/bug946519-v1.2

Bug 944276: MMS workaround for problem with memory-backed blobs r=julienw(cherry picked from commit bd559ee748be267a80fff2bbdbd887c85af06eba)

add global comment to keep jshint happy
Merge pull request #15820 from davidflanagan/bug944276

Merge pull request #14547 from davidflanagan/bug946519-v1.2 r=julienw