Track thread activities in order to diagnose hangs.

base/process/process_win.cc

Index: base/process/process_win.cc
diff --git a/base/process/process_win.cc b/base/process/process_win.cc
index 8e508a1b1fbaa4496b8ba34cef30bb2903b8cda7..6629f4565a74fb5e019ad05e845feba09f65625e 100644
--- a/base/process/process_win.cc
+++ b/base/process/process_win.cc
@@ -4,6 +4,7 @@
 
 #include "base/process/process.h"
 
+#include "base/debug/activity_tracker.h"
 #include "base/logging.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/process/kill.h"
@@ -142,6 +143,9 @@ bool Process::WaitForExit(int* exit_code) {
 }
 
 bool Process::WaitForExitWithTimeout(TimeDelta timeout, int* exit_code) {
+  // Record the event that this thread is blocking upon (for hang diagnosis).
+  base::debug::ScopedProcessWaitActivity process_activity(this);
+
   // Limit timeout to INFINITE.
   DWORD timeout_ms = saturated_cast<DWORD>(timeout.InMilliseconds());
   if (::WaitForSingleObject(Handle(), timeout_ms) != WAIT_OBJECT_0)