See https://build.chromium.org/p/chromium.memory.full/builders/Linux%20MSan%20Tests/builds/704/steps/content_unittests%20on%20Ubuntu-12.04/logs/stdio for the full log:

[ RUN      ] UrlDataManagerBackendTest.ChromeNetworkErrorPageRequestFailed
==31445==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x9ef9c8e in GetResponseInfo content/browser/webui/url_data_manager_backend.cc:369:7
    #1 0xdef3ee4 in ?? net/url_request/url_request_job.cc:598:3
    #2 0x9ef82a5 in ?? content/browser/webui/url_data_manager_backend.cc:444:5
    #3 0xc8eeac6 in Run base/callback.h:388:12
    #4 0xc8eeac6 in RunTask base/debug/task_annotator.cc:54:0
    #5 0xc710fcb in RunTask base/message_loop/message_loop.cc:488:19
    #6 0xc712b07 in DeferOrRunPendingTask base/message_loop/message_loop.cc:497:5
    #7 0xc7146a8 in DoWork base/message_loop/message_loop.cc:621:13
    #8 0xc724512 in Run base/message_loop/message_pump_libevent.cc:217:31
    #9 0xc7897bc in Run base/run_loop.cc:35:10
    #10 0x3aaeb43 in TestBody content/browser/webui/url_data_manager_backend_unittest.cc:134:19
    #11 0xbdc1546 in HandleExceptionsInMethodIfSupported<testing::Test, void> testing/gtest/src/gtest.cc:2458:12
    #12 0xbdc1546 in Run testing/gtest/src/gtest.cc:2474:0
    #13 0xbdc4817 in Run testing/gtest/src/gtest.cc:2656:11
    #14 0xbdc603b in Run testing/gtest/src/gtest.cc:2774:28
    #15 0xbde31b1 in RunAllTests testing/gtest/src/gtest.cc:4647:43
    #16 0xbde21b4 in HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> testing/gtest/src/gtest.cc:2458:12
    #17 0xbde21b4 in Run testing/gtest/src/gtest.cc:4255:0
    #18 0xa2dca90 in RUN_ALL_TESTS testing/gtest/include/gtest/gtest.h:2237:46
    #19 0xa2dca90 in Run base/test/test_suite.cc:246:0
    #20 0xa332a6b in Run base/callback.h:388:12
    #21 0xa332a6b in LaunchUnitTestsInternal base/test/launcher/unit_test_launcher.cc:206:0
    #22 0xa3322c7 in LaunchUnitTests base/test/launcher/unit_test_launcher.cc:445:10
    #23 0x437d01f in main content/test/run_all_unittests.cc:24:10
    #24 0x7fd3e0ffa7ec in __libc_start_main /build/eglibc-oqps9y/eglibc-2.15/csu/libc-start.c:226:0
    #25 0x676658 in _start ??:0

  Uninitialized value was created by a heap allocation
    #0 0x6e08e2 in operator new(unsigned long) ??:0
    #1 0x9f01778 in MaybeCreateJob content/browser/webui/url_data_manager_backend.cc:546:12
    #2 0xdef625f in MaybeCreateJobWithProtocolHandler net/url_request/url_request_job_factory_impl.cc:60:22
    #3 0xdef8ae5 in CreateJob net/url_request/url_request_job_manager.cc:71:37
    #4 0xded64b0 in Start net/url_request/url_request.cc:536:49
    #5 0x3aaeb1a in TestBody content/browser/webui/url_data_manager_backend_unittest.cc:133:18
    #6 0xbdc1546 in HandleExceptionsInMethodIfSupported<testing::Test, void> testing/gtest/src/gtest.cc:2458:12
    #7 0xbdc1546 in Run testing/gtest/src/gtest.cc:2474:0
    #8 0xbdc4817 in Run testing/gtest/src/gtest.cc:2656:11
    #9 0xbdc603b in Run testing/gtest/src/gtest.cc:2774:28
    #10 0xbde31b1 in RunAllTests testing/gtest/src/gtest.cc:4647:43
    #11 0xbde21b4 in HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> testing/gtest/src/gtest.cc:2458:12
    #12 0xbde21b4 in Run testing/gtest/src/gtest.cc:4255:0
    #13 0xa2dca90 in RUN_ALL_TESTS testing/gtest/include/gtest/gtest.h:2237:46
    #14 0xa2dca90 in Run base/test/test_suite.cc:246:0
    #15 0xa332a6b in Run base/callback.h:388:12
    #16 0xa332a6b in LaunchUnitTestsInternal base/test/launcher/unit_test_launcher.cc:206:0
    #17 0xa3322c7 in LaunchUnitTests base/test/launcher/unit_test_launcher.cc:445:10
    #18 0x437d01f in main content/test/run_all_unittests.cc:24:10
    #19 0x7fd3e0ffa7ec in __libc_start_main /build/eglibc-oqps9y/eglibc-2.15/csu/libc-start.c:226:0

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/b/swarming/w/irAuR6rd/out/Release/content_unittests+0x9ef9c8e)
Exiting
[2633/4157] UrlDataManagerBackendTest.ChromeNetworkErrorPageRequestFailed (CRASHED)