See https://build.chromium.org/p/chromium.memory.fyi/builders/Windows%20Content%20Browser%20%28DrMemory%20full%29%20%284%29/builds/7638/steps/memory%20test%3A%20content_browsertests_7/logs/stdio:

Below is the report for drmemory wrapper PID=4152_18.
 It was used while running the `SitePerProcessIgnoreCertErrorsBrowserTest.PassiveMixedContentInIframe` test.
-----------------------------------------------------
Suppressions used:
  count name
      1 bug_347967_all_osmesa
      1 bug_571553
      1 bug_594829a
      1 bug_594829b
      1 bug_595093b
      1 http://crbug.com/371368
      1 http://crbug.com/371946
      1 https://github.com/DynamoRIO/drmemory/issues/113 rpcrt4.dll wildcard
      1 https://github.com/DynamoRIO/drmemory/issues/18 d
      1 https://github.com/DynamoRIO/drmemory/issues/412 h
      1 https://github.com/DynamoRIO/drmemory/issues/513 d
      1 https://github.com/DynamoRIO/dynamorio/issues/1443 (another instance)
      2 bug_595093a
      6 bug_595149
      7 https://github.com/DynamoRIO/drmemory/issues/68 a
     12  http://crbug.com/379000 
     12 http://crbug.com/487500b
     15 http://crbug.com/346993
     17 http://crbug.com/371942
     45 http://crbug.com/449989
     65 http://crbug.com/371357
-----------------------------------------------------
17:54:50 drmemory_analyze.py [INFO] Found 1 error reports
17:54:50 drmemory_analyze.py [INFO] Report #1
### BEGIN MEMORY TOOL REPORT (error hash=#7F1BDC62C75E9D19#)
UNADDRESSABLE ACCESS: reading 0x00000000-0x00000004 4 byte(s)
# 0 content.dll!content::FrameTreeNode::child_at                               [content\browser\frame_host\frame_tree_node.h:116]
# 1 content::SitePerProcessIgnoreCertErrorsBrowserTest_PassiveMixedContentInIframe_Test::RunTestOnMainThread [content\browser\site_per_process_browsertest.cc:6017]
# 2 content::ContentBrowserTest::RunTestOnMainThreadLoop                       [content\public\test\content_browser_test.cc:134]
# 3 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop                     [content\public\test\browser_test_base.cc:309]
# 4 content::ShellBrowserMainParts::PreMainMessageLoopRun                      [content\shell\browser\shell_browser_main_parts.cc:175]
# 5 content.dll!content::BrowserMainLoop::PreMainMessageLoopRun                [content\browser\browser_main_loop.cc:928]
# 6 content.dll!base::internal::Invoker<>::Run                                 [base\bind_internal.h:362]
# 7 content.dll!content::StartupTaskRunner::RunAllTasksNow                     [content\browser\startup_task_runner.cc:45]
# 8 content.dll!content::BrowserMainLoop::CreateStartupTasks                   [content\browser\browser_main_loop.cc:801]
# 9 content.dll!content::BrowserMainRunnerImpl::Initialize                     [content\browser\browser_main_runner.cc:139]
#10 ShellBrowserMain                                                           [content\shell\browser\shell_browser_main.cc:23]
#11 content::ShellMainDelegate::RunProcess                                     [content\shell\app\shell_main_delegate.cc:285]
#12 content.dll!content::RunNamedProcessTypeMain                               [content\app\content_main_runner.cc:367]
#13 content.dll!content::ContentMainRunnerImpl::Run                            [content\app\content_main_runner.cc:741]
#14 content.dll!content::ContentMain                                           [content\app\content_main.cc:19]
#15 content::BrowserTestBase::SetUp                                            [content\public\test\browser_test_base.cc:282]
#16 content::ContentBrowserTest::SetUp                                         [content\public\test\content_browser_test.cc:92]
#17 testing::internal::HandleExceptionsInMethodIfSupported<>                   [testing\gtest\src\gtest.cc:2458]
Note: @0:02:52.857 in thread 644
Note: instruction: mov    (%ecx,%eax,4) -> %eax
The report came from the `SitePerProcessIgnoreCertErrorsBrowserTest.PassiveMixedContentInIframe` test.
Suppression (error hash=#7F1BDC62C75E9D19#):
  For more info on using suppressions see http://dev.chromium.org/developers/how-tos/using-drmemory#TOC-Suppressing-error-reports-from-the-
{
UNADDRESSABLE ACCESS
name=<insert_a_suppression_name_here>
content.dll!content::FrameTreeNode::child_at
*!content::SitePerProcessIgnoreCertErrorsBrowserTest_PassiveMixedContentInIframe_Test::RunTestOnMainThread
*!content::ContentBrowserTest::RunTestOnMainThreadLoop
*!content::BrowserTestBase::ProxyRunTestOnMainThreadLoop
*!content::ShellBrowserMainParts::PreMainMessageLoopRun
content.dll!content::BrowserMainLoop::PreMainMessageLoopRun
content.dll!base::internal::Invoker<>::Run
content.dll!content::StartupTaskRunner::RunAllTasksNow
content.dll!content::BrowserMainLoop::CreateStartupTasks
content.dll!content::BrowserMainRunnerImpl::Initialize
*!ShellBrowserMain
*!content::ShellMainDelegate::RunProcess
content.dll!content::RunNamedProcessTypeMain
content.dll!content::ContentMainRunnerImpl::Run
content.dll!content::ContentMain
*!content::BrowserTestBase::SetUp
*!content::ContentBrowserTest::SetUp
*!testing::internal::HandleExceptionsInMethodIfSupported<>
}
### END MEMORY TOOL REPORT (error hash=#7F1BDC62C75E9D19#)


Emily, can you please take a look?