Remove fixed chromebot crash signatures.

chrome/test/data/reliability/known_crashes.txt

 # This file contains known patterns of crash signatures. One pattern per line.
 #
 # A crash signature is the concatenation of the top N functions, delimited by
 # '___', in chrome.dll on the crash stack. All characters are lower case.
 #
 # We use crash signature patterns as our list of known crashes. A crash
 # signature pattern is a string that can be used to identify a known crash. We
 # use the notion of patterns because crashes with the same root cause can often
 # differ somewhat in their crash stacks. A pattern is intended to be a
 # generalized, yet still identifying, form of a particular crash. Usually a
@@ skipping 31 matching lines @@
 
 # 15620
 PREFIX : browser::processpendingtabs___browser::clearunloadstate
 
 # 47207
 PREFIX : messageloop::runtask___messageloop::deferorrunpendingtask___messageloop::dodelayedwork___base::messagepumpforio::dorunloop___base::messagepumpwin::run___messageloop::runinternal___messageloop::run___base::thread::run___base::thread::threadmain___`anonymous namespace'::threadfunc
 
 # 48712
 PREFIX : npapi::plugininstance::npp_newstream
 
-# 49254
-SUBSTRING : std::_tree<std::_tmap_traits<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,net::internal::clientsocketpoolbasehelper::group,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<std::pair<std::basic_string<char,std::char_traits<char>,std::allocator<char> > const ,net::internal::clientsocketpoolbasehelper::group> >,0> >::erase___net::internal::clientsocketpoolbasehelper::onavailablesocketslot
-SUBSTRING : std::_tree<std::_tmap_traits<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,net::internal::clientsocketpoolbasehelper::group,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<std::pair<std::basic_string<char,std::char_traits<char>,std::allocator<char> > const ,net::internal::clientsocketpoolbasehelper::group> >,0> >::_lbound___std::_tree<std::_tmap_traits<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,net::internal::clientsocketpoolbasehelper::group,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<std::pair<std::basic_string<char,std::char_traits<char>,std::allocator<char> > const ,net::internal::clientsocketpoolbasehelper::group> >,0> >::find___net::internal::clientsocketpoolbasehelper::onavailablesocketslot
-
-
 # 49271
 PREFIX : messageloop::posttask_helper___messageloop::posttask___disk_cache::inflightio::oniocomplete___disk_cache::backendio::executebackendoperation___messageloop::runtask___messageloop::dowork___base::messagepumpforio::dorunloop___base::messagepumpwin::run___messageloop::runinternal___messageloop::run___base::thread::run___base::thread::threadmain___`anonymous namespace'::threadfunc
 
 # 49384
 PREFIX : anonymous namespace'::cachecreator::docallback___`anonymous namespace'::cachecreator::oniocomplete___disk_cache::inflightbackendio::onoperationcomplete___disk_cache::inflightio::invokecallback___disk_cache::backgroundio::oniosignalled___messageloop::runtask___messageloop::dowork___base::messagepumpforio::dorunloop___base::messagepumpwin::run___messageloop::runinternal___messageloop::run___base::thread::run___base::thread::threadmain___`anonymous namespace'::threadfunc
 
 # 49409
 PREFIX : std::basic_string<char,std::char_traits<char>,std::allocator<char> >::assign___fieldtriallist::statestostring___browserrenderprocesshost::appendrenderercommandline___browserrenderprocesshost::init___renderviewhost::createrenderview___tabcontents::createrenderviewforrendermanager___renderviewhostmanager::initrenderview___renderviewhostmanager::creatependingrenderview___renderviewhostmanager::updaterendererstatefornavigate___renderviewhostmanager::navigate___tabcontents::navigatetopendingentry___navigationcontroller::navigatetopendingentry___navigationcontroller::loadentry___navigationcontroller::loadurl___browser::openurlatindex___browser::openurlfromtab___browser::openurl___automationprovider::navigatetourlblockuntilnavigationscomplete___automationprovider::navigatetourl___ipc
 
 # 39356
 PREFIX: renderwidgethost::onmsgupdaterect___ipc::messagewithtuple<tuple1<viewhostmsg_updaterect_params> >::dispatch<renderwidgethost,void (__thiscall renderwidgethost::*)(viewhostmsg_updaterect_params const &)>___renderwidgethost::onmessagereceived___renderviewhost::onmessagereceived___browserrenderprocesshost::onmessagereceived___renderwidgethelper::updatemsgproxy::run___messageloop::runtask___messageloop::dowork___base::messagepumpforui::dorunloop___base::messagepumpwin::runwithdispatcher___messageloop::runinternal___messageloopforui::run___`anonymous namespace'::runuimessageloop___browsermain___chromemain___maindllloader::launch___wwinmain_____tmaincrtstartup
 
 # 52346
 PREFIX : tabcontentsview::deactivate___renderwidgethost::onmessagereceived___renderviewhost::onmessagereceived___browserrenderprocesshost::onmessagereceived
 
 # 53076
 PREFIX : tabcontentsview::activate___renderwidgethost::onmessagereceived___renderviewhost::onmessagereceived___browserrenderprocesshost::onmessagereceived