SyzyASAN: Block for crash handler startup as temporary workaround for startup hang

chrome/app/chrome_exe_main_win.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <windows.h>
 #include <malloc.h>
 #include <shellscalingapi.h>
 #include <stddef.h>
 #include <tchar.h>
 
@@ skipping 180 matching lines @@
 
       // Return if we changed anything so that we can restart.
       return tokens.size() != initial_size && result == ERROR_SUCCESS;
     }
   }
   return false;
 }
 
 }  // namespace
 
+#if defined(SYZYASAN)
+// This is in chrome_elf.
+extern "C" void BlockUntilHandlerStartedImpl();
+#endif  // SYZYASAN
+
 #if !defined(WIN_CONSOLE_APP)
 int APIENTRY wWinMain(HINSTANCE instance, HINSTANCE prev, wchar_t*, int) {
 #else
 int main() {
   HINSTANCE instance = GetModuleHandle(nullptr);
 #endif
   install_static::InstallDetails::InitializeFromPrimaryModule(
       chrome::kChromeElfDllName);
 
   // Initialize the CommandLine singleton from the environment.
@@ skipping 14 matching lines @@
   if (process_type == crash_reporter::switches::kCrashpadHandler) {
     return crash_reporter::RunAsCrashpadHandler(
         *base::CommandLine::ForCurrentProcess());
   }
 
   const base::TimeTicks exe_entry_point_ticks = base::TimeTicks::Now();
 
   // Signal Chrome Elf that Chrome has begun to start.
   SignalChromeElf();
 
+#if defined(SYZYASAN)
+  if (process_type.empty()) {
+    // This is a temporary workaround for a race during startup with the
+    // syzyasan_rtl.dll. See https://crbug.com/675710.
+    BlockUntilHandlerStartedImpl();
+  }
+#endif  // SYZYASAN
+
   // The exit manager is in charge of calling the dtors of singletons.
   base::AtExitManager exit_manager;
 
   EnableHighDPISupport();
 
   if (AttemptFastNotify(*command_line))
     return 0;
 
   RemoveAppCompatFlagsEntry();
 
   // Load and launch the chrome dll. *Everything* happens inside.
   VLOG(1) << "About to load main DLL.";
   MainDllLoader* loader = MakeMainDllLoader();
   int rc = loader->Launch(instance, exe_entry_point_ticks);
   loader->RelaunchChromeBrowserWithNewCommandLineIfNeeded();
   delete loader;
   return rc;
 }