Unexpected Failures:
* loading.desktop.network_service/AirBnB_cold
* loading.desktop.network_service/AirBnB_warm
* loading.desktop.network_service/Kenh14_cold
* loading.desktop.network_service/Kenh14_warm
* loading.desktop.network_service/Taobao_cold
* loading.desktop.network_service/Taobao_warm

Sample Failing Build (might be flaky since my bisect points to a different CL):
* https://ci.chromium.org/buildbot/chromium.perf.fyi/Mojo%20Linux%20Perf/6459

Bisect Points to:
* f34bba7c38758baf556aef6649fdd97f1b8a41a9 - Simplify in-process URLRequestContext creation with the NetworkService.
  - It seems that the test was revealed by the CL intentionally.

Reproduce:
* tools/perf/run_benchmark loading.desktop --browser=default --story-filter=AirBnB_cold --pageset-repeat=1 --extra-browser-args=--enable-features=NetworkService

Sample Log:
```
********************************************************************************
	Operating system: Linux
	                  0.0.0 Linux 3.13.0-141-generic #190-Ubuntu SMP Fri Jan 19 12:52:38 UTC 2018 x86_64
	CPU: amd64
	     family 6 model 94 stepping 3
	     1 CPU
	
	GPU: UNKNOWN
	
	Crash reason:  SIGSEGV
	Crash address: 0x0
	Process uptime: not available
	
	Thread 3 (crashed)
	 0  chrome!content::P2PSocketDispatcherHost::OnGetHostAddress(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int) [socket_dispatcher_host.cc : 82 + 0x0]
	    rax = 0x0000105ce1c87a00   rdx = 0x00007f7a01c746b0
	    rcx = 0x000000000000008d   rbx = 0x0000105ce1c87a00
	    rsi = 0x00007f79f2141e08   rdi = 0x00007f79f2141e30
	    rbp = 0x00007f79f2141eb0   rsp = 0x00007f79f2141df0
	     r8 = 0x0000105ce1de2d08    r9 = 0x000000000000000c
	    r10 = 0x0000000000000004   r11 = 0x00007f79fa3f9310
	    r12 = 0x0000000000000000   r13 = 0x0000105ce19d25b0
	    r14 = 0x00007f79f2141e30   r15 = 0x00007f79f2141e08
	    rip = 0x00007f7a0298ec25
	    Found by: given as instruction pointer in context
	 1  chrome!content::P2PSocketDispatcherHost::OnMessageReceived(IPC::Message const&) [tuple.h : 52 + 0x8]
	    rbx = 0x00007f7a07e5fc20   rbp = 0x00007f79f2142090
	    rsp = 0x00007f79f2141ec0   r12 = 0x00007f79f21422b8
	    r13 = 0x00007f7a00810df8   r14 = 0x0000105ce1aa46c0
	    r15 = 0x0000000000000000   rip = 0x00007f7a0298e086
	    Found by: call frame info
	 2  chrome!content::BrowserMessageFilter::Internal::OnMessageReceived(IPC::Message const&) [browser_message_filter.cc : 93 + 0x6]
	    rbx = 0x00007f7a080ff2c0   rbp = 0x00007f79f2142100
	    rsp = 0x00007f79f21420a0   r12 = 0x0000105ce1b16980
	    r13 = 0x00007f7a00810df8   r14 = 0x00007f79f21422b8
	    r15 = 0x0000000000000000   rip = 0x00007f7a025991da
	    Found by: call frame info
	 3  chrome!IPC::MessageFilterRouter::TryFilters(IPC::Message const&) [message_filter_router.cc : 22 + 0x6]
	    rbx = 0x0000000000000000   rbp = 0x00007f79f2142140
	    rsp = 0x00007f79f2142110   r12 = 0x00007f7a08122500
	    r13 = 0x00007f7a0080f597   r14 = 0x00007f79f21422b8
	    r15 = 0x0000105ce19efb38   rip = 0x00007f7a03e0bb36
	    Found by: call frame info
	 4  chrome!IPC::ChannelProxy::Context::TryFilters(IPC::Message const&) [ipc_channel_proxy.cc : 86 + 0x5]
	    rbx = 0x0000105ce197fb40   rbp = 0x00007f79f21421b0
	    rsp = 0x00007f79f2142150   r12 = 0x00007f7a080f5de0
	    r13 = 0x00007f79f21422b8   r14 = 0x00007f79f21422b8
	    r15 = 0x00007f79f21422b8   rip = 0x00007f7a03dff1d0
	    Found by: call frame info
	 5  chrome!IPC::ChannelProxy::Context::OnMessageReceived(IPC::Message const&) [ipc_channel_proxy.cc : 121 + 0x5]
	    rbx = 0x0000105ce197fb40   rbp = 0x00007f79f21421d0
	    rsp = 0x00007f79f21421c0   r12 = 0x00007f7a080f5de0
	    r13 = 0x00007f7a00504563   r14 = 0x00007f79f21422b8
	    r15 = 0x00007f79f21422b8   rip = 0x00007f7a03dff332
	    Found by: call frame info
```

Going to disable to test.