Generate dumps for relevant renderers when users kill a hung pepper plugin.

ppapi/shared_impl/ppapi_message_tracker.cc

Index: ppapi/shared_impl/ppapi_message_tracker.cc
diff --git a/ppapi/shared_impl/ppapi_message_tracker.cc b/ppapi/shared_impl/ppapi_message_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4fba69f492ebdf0c77142058580589914232813a
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+++ b/ppapi/shared_impl/ppapi_message_tracker.cc
@@ -0,0 +1,47 @@
+// Copyright (c) 2012 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 "ppapi/shared_impl/ppapi_message_tracker.h"
+
+#include "base/logging.h"
+#include "base/memory/singleton.h"
+
+namespace ppapi {
+
+//static
+PpapiMessageTracker* PpapiMessageTracker::GetInstance() {
+  return Singleton<PpapiMessageTracker>::get();
+}
+
+PpapiMessageTracker::PpapiMessageTracker() : enter_count_(0) {
+}
+
+PpapiMessageTracker::~PpapiMessageTracker() {
+}
+
+void PpapiMessageTracker::EnterMessageHandling() {
+  base::AutoLock auto_lock(lock_);
+  enter_count_++;
+}
+
+void PpapiMessageTracker::ExitMessageHandling() {
+  base::AutoLock auto_lock(lock_);
+  DCHECK_GT(enter_count_, 0);
+  enter_count_--;
+}
+
+bool PpapiMessageTracker::IsHandlingMessage() {
+  base::AutoLock auto_lock(lock_);
+  return enter_count_ > 0;
+}
+
+ScopedTrackPpapiMessage::ScopedTrackPpapiMessage() {
+  PpapiMessageTracker::GetInstance()->EnterMessageHandling();
+}
+
+ScopedTrackPpapiMessage::~ScopedTrackPpapiMessage() {
+  PpapiMessageTracker::GetInstance()->ExitMessageHandling();
+}
+
+}  // namespace ppapi