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..a645432fe768d3029b9736e51c3055481f0f0210 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

[engedy, 2014/05/16 15:19:58]

nit: period to the end of the comment.

[battre, 2014/05/16 15:58:37]

Done.

+#include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 
@@ -48,6 +50,22 @@ 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 stacktrack of the destruction in

[engedy, 2014/05/16 15:19:58]

nit: s/stacktrack/stack trace

[battre, 2014/05/16 15:58:37]

Done.

+    // pref_service_destruction_. We save this on the stack in the minidump to
+    // understand what happens.
+    char tmp[2048];
+    const int copy =
+        std::min<int>(sizeof(tmp) - 1, pref_service_destruction_.length());

[engedy, 2014/05/16 15:19:58]

Could we use strncat() here, like so:

char tmp[2048] = {};
strncat(tmp, pref_service_destruction_.c_str(), sizeof(tmp)-1);

[battre, 2014/05/16 15:58:37]

Done.

+    memcpy(tmp, pref_service_destruction_.c_str(), copy);
+    tmp[copy] = '\0';
+    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 +99,12 @@ void PrefChangeRegistrar::OnPreferenceChanged(PrefService* service,
     observers_[pref].Run(pref);
 }
 
+// TODO(battre): Delete this. See crbug.com/373435.
+void PrefChangeRegistrar::SetPrefServiceDestructionTrace(
+    const std::string& stacktrace) {

[engedy, 2014/05/16 15:19:58]

nit: stack_trace.

[battre, 2014/05/16 15:58:37]

Done.

+  pref_service_destruction_ = stacktrace;
+}
+
 void PrefChangeRegistrar::InvokeUnnamedCallback(const base::Closure& callback,
                                                 const std::string& pref_name) {
   callback.Run();