Store a stacktrace of PrefService destruction in PrefChangeRegistrar

base/prefs/pref_change_registrar.cc

Index: base/prefs/pref_change_registrar.cc
diff --git a/base/prefs/pref_change_registrar.cc b/base/prefs/pref_change_registrar.cc
index 28ac37403435f7428670cc032f6f603e7f6ecda6..03768dc9d0a3350aeb71b023e17b848841fbe5ee 100644
--- a/base/prefs/pref_change_registrar.cc
+++ b/base/prefs/pref_change_registrar.cc
@@ -5,6 +5,8 @@
 #include "base/prefs/pref_change_registrar.h"
 
 #include "base/bind.h"
+// TODO(battre): Delete this. See crbug.com/373435.
+#include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 
@@ -48,6 +50,19 @@ void PrefChangeRegistrar::Remove(const char* path) {
 }
 
 void PrefChangeRegistrar::RemoveAll() {
+  // TODO(battre): Delete this. See crbug.com/373435.
+  if (!observers_.empty() && !pref_service_destruction_.empty()) {
+    // The PrefService is already destroyed, so the following call to
+    // service_->RemovePrefObserver would crash anyway. When the PrefService
+    // was destroyed, it stored a stack trace of the destruction in
+    // pref_service_destruction_. We save this on the stack in the minidump to
+    // understand what happens.
+    char tmp[2048] = {};
+    strncat(tmp, pref_service_destruction_.c_str(), sizeof(tmp) - 1u);
+    base::debug::Alias(tmp);
+    CHECK(false) << tmp;
+  }
+
   for (ObserverMap::const_iterator it = observers_.begin();
        it != observers_.end(); ++it) {
     service_->RemovePrefObserver(it->first.c_str(), this);
@@ -81,6 +96,12 @@ void PrefChangeRegistrar::OnPreferenceChanged(PrefService* service,
     observers_[pref].Run(pref);
 }
 
+// TODO(battre): Delete this. See crbug.com/373435.
+void PrefChangeRegistrar::SetPrefServiceDestructionTrace(
+    const std::string& stack_trace) {
+  pref_service_destruction_ = stack_trace;
+}
+
 void PrefChangeRegistrar::InvokeUnnamedCallback(const base::Closure& callback,
                                                 const std::string& pref_name) {
   callback.Run();