Bug 784739 - Switch from NULL to nullptr in docshell/; r=ehsan

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extra : rebase_source : 3fd9a17d97fc1f11b9b127f14d8787f18c92f5a9
Bug 784739 - Switch from NULL to nullptr in embedding/; r=ehsan

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extra : rebase_source : ccdffce1019f7a5f8f5d12fb600aff5da2831528