Code to collect issue 97285 debugging info for crash reports.

content/public/common/content_debug_logging.h

+// 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_CONTENT_DEBUG_LOGGING_H_
+#define CONTENT_PUBLIC_BROWSER_CONTENT_DEBUG_LOGGING_H_
+
+#include "content/common/content_export.h"
+
+#include <string>
+#include <vector>
+
+// When debugging single processes, a common technique is to store
+// breakpad keys which can be analyzed from crashes.  That technique
+// does not work well for multi-process bugs.  This code can
+// be used to implement a ring buffer in the browser which stores the
+// most-recent N (browser-defined) messages relating to a bug.
+//
+// The intent is that users will call RecordMsg() to record info for
+// the bug, and GetMessages() to fetch the recorded info.  In the
+// browser process, these will be backed by a local data structure.
+// In other processes, they will be backed by messages forwarding to
+// the browser process.
+
+// TODO(shess): Since bug notes will be distributed across the code,
+// it would be inconvenient to require some other include to have
+// kBugNNNNN constants for users to use.  Those could be in this file,
+// but for now they're a DCHECK in chrome_delegate_main.cc (which
+// implements the actual storage).
+
+namespace content {
+namespace debug {
+
+// RecordMsg() and GetMessages() forward to the handlers set by
+// RegisterMessageHandlers().  If no handlers are set (or NULL
+// handlers are set), the messages are simply dropped.
+//
+// If GetMessages() returns false, there was no handler (or the
+// handler was unable to get messages).  *msgs will be cleared.  If
+// GetMessages() returns true, zero or more of the most recent
+// messages previously sent to RecordMsg() will be in *msgs, in the
+// order recorded, mod things like forwarded delay between processes.
+CONTENT_EXPORT void RecordMsg(int bug_id, const std::string& msg);
+CONTENT_EXPORT bool GetMessages(int bug_id, std::vector<std::string>* msgs);
+
+// Used to register handlers which will differ per process.
+typedef void RecordMsgFn(int bug_id, const std::string& msg);
+typedef bool GetMessagesFn(int bug_id, std::vector<std::string>* msgs);
+CONTENT_EXPORT void RegisterMessageHandlers(RecordMsgFn* record_handler,
+                                            GetMessagesFn* get_handler);
+
+// TODO(shess): It would be convenient to expose functions to do things like:
+// - load values into breakpad.
+// - load values into breakpad and dump without crashing.
+// - load values into breakpad and crash.
+// - log values to the console.
+// But this is mostly Chromium-level stuff.
+
+}  // namespace debug
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_CONTENT_DEBUG_LOGGING_H_