CrOS: Add print statements to help debug BrowserProcessImpl::Unpin crash.

chrome/browser/lifetime/keep_alive_registry.h

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_
 #define CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_
 
 #include <unordered_map>
 
 #include "base/macros.h"
@@ skipping 22 matching lines @@
   bool IsRestartAllowed() const;
   bool IsOriginRegistered(KeepAliveOrigin origin) const;
 
   void AddObserver(KeepAliveStateObserver* observer);
   void RemoveObserver(KeepAliveStateObserver* observer);
 
   // Returns whether restart would be allowed if all the keep alives for the
   // provided |origins| were not registered.
   bool WouldRestartWithout(const std::vector<KeepAliveOrigin>& origins) const;
 
+  // TODO(sammiequon): This is used to help debug the crash in crbug.com/660962.
+  // Remove this when the crash is fixed or if verified to not be related to
+  // this.
+  std::string ToString() const;

[sky, 2017/03/22 03:56:16]

How about naming this more specifically, possibly ToDebugString()?

+
  private:
   friend struct base::DefaultSingletonTraits<KeepAliveRegistry>;
   // Friend to be able to use Register/Unregister
   friend class ScopedKeepAlive;
   friend std::ostream& operator<<(std::ostream& out,
                                   const KeepAliveRegistry& registry);
 
   // TODO(dgn): Remove this when std::hash supports enums directly (c++14)
   // http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2148
   struct EnumClassHash {
@@ skipping 33 matching lines @@
   // Number of registered keep alives that have KeepAliveRestartOption::ENABLED.
   int restart_allowed_count_;
 
   base::ObserverList<KeepAliveStateObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(KeepAliveRegistry);
 };
 
 
 #endif  // CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_