[bgmode] Log the unpin stack trace to Crash Keys

chrome/common/crash_keys.h

 // Copyright (c) 2013 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_COMMON_CRASH_KEYS_H_
 #define CHROME_COMMON_CRASH_KEYS_H_
 
 #include <stddef.h>
 
 #include <set>
@@ skipping 50 matching lines @@
 extern const char kExtensionID[];
 // The total number of installed extensions, recorded in case it exceeds
 // kExtensionIDMaxCount. Also used in chrome/app, but defined here to avoid
 // a common->app dependency.
 extern const char kNumExtensionsCount[];
 
 // Type of shutdown. The value is one of "close" for WINDOW_CLOSE,
 // "exit" for BROWSER_EXIT, or "end" for END_SESSION.
 extern const char kShutdownType[];
 
+// Stack trace associated to the browser being unpinned and starting the
+// shutdown sequence. The value is set when we trigger a browser crash due to an
+// invalid attempt to Pin the browser process after that.
+extern const char kBrowserUnpinTrace[];
+
 // GPU information.
 #if !defined(OS_ANDROID)
 extern const char kGPUVendorID[];
 extern const char kGPUDeviceID[];
 #endif
 extern const char kGPUDriverVersion[];
 extern const char kGPUPixelShaderVersion[];
 extern const char kGPUVertexShaderVersion[];
 #if defined(OS_MACOSX)
 extern const char kGPUGLVersion[];
@@ skipping 67 matching lines @@
 // Numbers of active views.
 extern const char kViewCount[];
 
 // TEMPORARY: The encoder/frame details at the time a zero-length encoded frame
 // was encountered.  http://crbug.com/519022
 extern const char kZeroEncodeDetails[];
 
 }  // namespace crash_keys
 
 #endif  // CHROME_COMMON_CRASH_KEYS_H_