Bug 1400466 - Cache the information loaded from src_comp.xdb into a structured...

Bug 1400466 - Cache the information loaded from src_comp.xdb into a structured clone buffer, r=jonco

Note that this requires some enhancements to the JS engine to support reading and writing structured clone data from/to files.

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extra : rebase_source : 444a2d407bd231efbba4b6b648eeb151f02177db