Import json by default, then simplejson.

tools/perf_expectations/perf_expectations.json

 {"linux-release-hardy/dhtml/commit_charge/cc": {"reva": 63231, "revb": 64325, "improve": -6947, "regress": 25528, "sha1": "0e22e67a"},
  "linux-release-hardy/dhtml/processes/proc_": {"improve": 0, "regress": 0, "sha1": "696fcb0f"},
  "linux-release-hardy/dhtml/times/t": {"reva": 80750, "revb": 81211, "improve": -66, "regress": 35, "sha1": "900460fd"},
  "linux-release-hardy/dhtml/total_byte_b/IO_b": {"reva": 76562, "revb": 76684, "improve": 3612, "regress": 4135, "sha1": "757631c0"},
  "linux-release-hardy/dhtml/total_byte_r/IO_r": {"reva": 71820, "revb": 73091, "improve": -42, "regress": -38, "sha1": "2fa955ce"},
  "linux-release-hardy/dhtml/total_op_b/IO_op_b": {"reva": 70127, "revb": 76230, "improve": 26261, "regress": 40613, "sha1": "1658213e"},
  "linux-release-hardy/dhtml/total_op_r/IO_op_r": {"reva": 80853, "revb": 81211, "improve": 60, "regress": 698, "sha1": "17890f30"},
  "linux-release-hardy/dhtml/vm_rss_final_b/vm_rss_f_b": {"reva": 78369, "revb": 79175, "improve": 11101593, "regress": 12855092, "sha1": "46e5fb4d"},
  "linux-release-hardy/dhtml/vm_rss_final_r/vm_rss_f_r": {"reva": 74289, "revb": 75628, "improve": 20024115, "regress": 24295220, "sha1": "ffc77cea"},
  "linux-release-hardy/dhtml/vm_rss_final_t/vm_rss_f_t": {"reva": 78369, "revb": 79175, "improve": 32534323, "regress": 38320128, "sha1": "7ff7cf40"},
@@ skipping 78 matching lines @@
  "xp-release-dual-core/moz/vm_peak_b/vm_pk_b": {"reva": 79228, "revb": 79498, "improve": -3165389, "regress": -1529241, "sha1": "9d7d2c9c"},
  "xp-release-dual-core/moz/vm_peak_r/vm_pk_r": {"reva": 79665, "revb": 81211, "improve": -477389, "regress": 1522484, "sha1": "1bf70d99"},
  "xp-release-dual-core/startup/warm/t": {"reva": 76825, "revb": 77094, "improve": -107, "regress": 141, "sha1": "e0dcf672"},
  "xp-release-dual-core/v8_benchmark/score/score": {"reva": 68696, "revb": 69071, "improve": 892, "regress": -668, "sha1": "75a383d3"},
  "xp-release-single-core/dhtml/times/t": {"reva": 78005, "revb": 79501, "improve": -489, "regress": -273, "sha1": "3d4e9971"},
  "xp-release-single-core/intl1/times/t": {"reva": 81197, "revb": 82805, "improve": -2953, "regress": -1926, "sha1": "a0dc047a"},
  "xp-release-single-core/intl2/times/t": {"reva": 78006, "revb": 79149, "improve": -1566, "regress": -871, "sha1": "90946d93"},
  "xp-release-single-core/morejs/times/t": {"reva": 81028, "revb": 81209, "improve": -417, "regress": -264, "sha1": "8ce9af86"},
  "xp-release-single-core/moz/times/t": {"reva": 75758, "revb": 76221, "improve": -1705, "regress": 3304, "sha1": "b615a416"},
  "xp-release-single-core/startup/times/t": {"improve": -9, "regress": 9, "sha1": "b1bf03da"},
- "xp-release/sizes/chrome.dll/chrome.dll": {"reva": 82752, "revb": 82805, "type": "absolute", "improve": 31857740, "regress": 35223015, "sha1": "499e878b"},
- "xp-release/sizes/chrome.exe/chrome.exe": {"reva": 81814, "revb": 82805, "type": "absolute", "improve": 1068134, "regress": 1180570, "sha1": "a17d7ab1"},
- "xp-release/sizes/mini_installer.exe/mini_installer.exe": {"reva": 82343, "revb": 82805, "type": "absolute", "improve": 17126630, "regress": 19045018, "sha1": "ec604130"},
- "xp-release/sizes/setup.exe/setup.exe": {"reva": 81852, "revb": 82805, "type": "absolute", "improve": 1138662, "regress": 1258522, "sha1": "4ecff95d"},
+ "xp-release/sizes/chrome.dll/chrome.dll": {"reva": 82752, "revb": 82805, "type": "absolute", "improve": 31857740, "regress": 35223015, "sha1": "be0edad1"},
+ "xp-release/sizes/chrome.exe/chrome.exe": {"reva": 81814, "revb": 82805, "type": "absolute", "improve": 1068134, "regress": 1180570, "sha1": "e56118d2"},
+ "xp-release/sizes/mini_installer.exe/mini_installer.exe": {"reva": 82343, "revb": 82805, "type": "absolute", "improve": 17126630, "regress": 19045018, "sha1": "204c5a96"},
+ "xp-release/sizes/setup.exe/setup.exe": {"reva": 81852, "revb": 82805, "type": "absolute", "improve": 1138662, "regress": 1258522, "sha1": "f1de9ae7"},
  "load": true
 }