Remove logs in in persistent_cache.cc that look like possible memory corruption #62468
Description
There appears to be a bad pointer ref in shell/common/persistent_cache.cc, as the following logs were seen in the backdrop_filter_perf_ios__timeline_summary devicelab test (against commit ddb6d9d):
2020-07-28T20:17:25.626431: stdout: [ +238 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAECA4AAAAAAAAABGAABAAOAAEIACUAAGAH7777777777777777777777777EAAAKAAAAAAAAAAAAAAAEAAAAAYAAWIA
2020-07-28T20:17:25.671005: stderr: [ +44 ms] VMServiceFlutterDriver: Connected to Flutter application.
2020-07-28T20:17:26.074907: stdout: [ +403 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAACAYAAAAAIAAABGAABAD7777777777777777776FAABYAAAAAAAAAAAAAAAIAAAABEABMQA
2020-07-28T20:17:26.194524: stdout: [ +119 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAECA4AAAAIAAAABGAABAAOAAEIACUAAGAH7777777777777777777777777EAAAKAAAAAAAAAAAAAAAEAAAAAYAAWIA
2020-07-28T20:17:26.264018: stdout: [ +69 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAECAYAAAAAAAAAACAAAAAJQAAIADQABCAAPAAKAAAAAAAABIAA2AAAAAAAAAAAAAAACAAAAAKAALEAA
2020-07-28T20:17:26.421218: stdout: [ +157 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAACAYAABAAIAAABGAABAD777777777777YZAAAAAFAABYAAAAAAAAAAAAAAAIAAAABEABMQA
2020-07-28T20:17:26.515747: stdout: [ +94 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAACAUAABEAAAAABGAABAAOAAAYABQAEIAAAAAAAAAAAAAAAEAAAAAOAAWIA
2020-07-28T20:17:26.660058: stdout: [ +144 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAECAUAAAAAAAAABGAABAAOAAEIADQAAGAAQABNQAAAAAAAAAAAAAABAAAAAEAAFSAA
2020-07-28T20:17:26.781891: stdout: [ +121 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAACAYAABEAJAAABGAABAAOAAEIA777777YZAAAAAFAABYAAAAAAAAAAAAAAAIAAAABEABMQA
2020-07-28T20:17:26.893141: stdout: [ +111 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAECAUAAAEYAAEABYAARAANQAAQAAAAAAAAMABEQAAAAAAAAAAAAAABAAAAAEAAFSAA
2020-07-28T20:17:27.033490: stdout: [ +140 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAMCBEAAAAAAAAAEOAAAAAJQAAIA777777Y4AAIQB7777777777777777777EAAFYAAAAAAAAAAAAAAHSAAAAAYAABQAAQAAAAAAAAAAAAQAAAAEAACZAA
2020-07-28T20:17:27.207236: stdout: [ +173 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAMCBEAAAAAAAAAEOAQAAAJQAAIA777777Y4AAIQB7777777777777777777EAAFYAAAAAAAAAAAAAAHSAAAAAYAABQAAQAAAAAAAAAAAAQAAAAEAACZAA
2020-07-28T20:17:27.278432: stdout: [ +71 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAEBAUAAAEYAAEABYAARAANQAAQAAAAAAAAMABEQAAAAAAAAAAAAAABAAAAAEAAFSAA
2020-07-28T20:17:27.298735: stdout: [ +20 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAEBA4AAAAAAAEABGAABAAOAAEIACUAAGAH7777777777777777777777777EAAAKAAAAAAAAAAAAAAAEAAAAAYAAWIA
2020-07-28T20:17:27.406361: stdout: [ +107 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAEBA4AAAAAAAAAEOAAAAAJQAAIA777777Y4AAIQB7777777777777777777EAAFYAAAAAAAAAAAAAAAEAAAAAYAAWIA
2020-07-28T20:17:27.484116: stdout: [ +77 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAEBAYAAAAAAAAAACAAAAAJQAAIADQABCAAPAAKAAAAAAAABIAA2AAAAAAAAAAAAAAACAAAAAKAALEAA
2020-07-28T20:17:27.835420: stdout: [ +351 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZAAAEBA4AAAAAAAAAEOAQAAAJQAAIA777777Y4AAIQB7777777777777777777EAAFYAAAAAAAAAAAAAAAEAAAAAYAAWIA
2020-07-28T20:17:27.835593: stdout: [ ] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZACAEBCAAAAAAAAAAGOAIAAAJQAAIACIAAAAA4AAIQAEYAAEAP777777777777EAAFYAAAAAAAAAYAAAACYACTAACAAAAAGQADQAAIAAAAAPAAHQAAIAAAAAAQAAAAAMAAAACMAAQAABAAAAAAAAAAAAADYAB4AA6AAPABAAAAAAYAAAAGQACAAACAAAAAAAAAAAACAAAAA6AALEAA
2020-07-28T20:17:28.137578: stdout: [ +301 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZACAEBBYAAAAAAAAACOAAAAAJQAAIA7777777777776EYAAEAP777777777777EAAFYAAAAAAAAAAAAAAAAIIDAAWAATYABAAAAAAAAAAAAABBAMADYAB4AACAAAAAAAAAAAANAAAAAAAAAAAAAIIDABKAAAQAAQAAAAAAAAAAAAQAAAAGQACZAA
2020-07-28T20:17:28.484525: stdout: [ +346 ms] [VERBOSE0:persistent_cache.cc(270)] PersistentCache::load failed: CAZACAABBYAAAAAAAAACOAAAAAJQAAIA7777777777776EYAAEAP777777777777EAAFYAAAAAAAAAAAAEAAAIIDAAWAATYABEAAAAAAAAAQAABBAMADYAB4AACQAAAABQAAAAAAAAAQAABBAMAFAABTAACAAAAAAAAAAAACAAAAAZAALEAA