New test infrastructure for producing verbose logs in failing tests.

chrome/test/base/file_logger_win.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 CHROME_TEST_BASE_FILE_LOGGER_WIN_H_
+#define CHROME_TEST_BASE_FILE_LOGGER_WIN_H_
+#pragma once
+
+#include <guiddef.h>
+
+#include "base/basictypes.h"
+#include "base/win/event_trace_controller.h"
+
+class FilePath;
+
+// A file logger instance captures LOG messages and trace events emitted via
+// Event Tracing for Windows (ETW) and sends them to a file.  The contents of
+// such a file can be sent to an output stream sometime later.
+//
+// Important usage notes (read this):
+// - Due to the nature of event generation, only one instance of this class may
+//   be initialized at a time, and only one file may be dumped at a time.

[grt (UTC plus 2), 2012/03/08 21:37:06]

oops, i need to remove reference to dumping here.
also, the comments here should point to the new reader/printer classes

+// - This class is not thread safe.
+// - This class uses facilities that require the process to run with admin
+//   rights; StartLogging() will return false if this is not the case.
+//
+// Initializing an instance will add the variable CHROME_ETW_LOGGING=1 to the
+// system-wide environment if it is not present.  In the case where it is not
+// already present, log messages will not be captured from currently running
+// instances of Chrome, Chrome Frame, or other providers that generate events
+// conditionally based on that environment variable.
+class FileLogger {
+ public:
+  enum EventProviderBits {
+    // Log messages from chrome.exe.
+    CHROME_LOG_PROVIDER         = 1 << 0,
+    // Log messages from npchrome_frame.dll.
+    CHROME_FRAME_LOG_PROVIDER   = 1 << 1,
+    // Log messages from the current process.
+    CHROME_TESTS_LOG_PROVIDER   = 1 << 2,
+    // Trace events.
+    CHROME_TRACE_EVENT_PROVIDER = 1 << 3,
+  };
+
+  static const uint32 kAllEventProviders = (CHROME_LOG_PROVIDER |
+                                            CHROME_FRAME_LOG_PROVIDER |
+                                            CHROME_TESTS_LOG_PROVIDER |
+                                            CHROME_TRACE_EVENT_PROVIDER);
+
+  FileLogger();
+  ~FileLogger();
+
+  // Initializes the instance to collect logs from all supported providers.
+  void Initialize();
+
+  // Initializes the instance to collect logs from the providers present in
+  // the given mask; see EventProviderBits.
+  void Initialize(uint32 event_provider_mask);
+
+  // Removes the system-wide CHROME_ETW_LOGGING=1 variable from the environment
+  // if it was inserted in Initialize().
+  void Uninitialize();
+
+  // Starts capturing logs from all providers into |log_file|.  The common file
+  // extension for such files is .etl.  Returns false if the session could not
+  // be started (e.g., if not running as admin).
+  bool StartLogging(const FilePath& log_file);
+
+  // Stops capturing logs.
+  void StopLogging();
+
+  // Returns true if logs are being captured.
+  bool is_logging() const {
+    return controller_.session_name() && *controller_.session_name();
+  }
+
+ private:
+  bool EnableProviders();
+  void DisableProviders();
+
+  void ConfigureChromeEtwLogging();
+  void RevertChromeEtwLogging();
+
+  base::win::EtwTraceController controller_;
+  uint32 event_provider_mask_;
+
+  // True if the system-wide variable CHROME_ETW_LOGGING=1 was inserted into the
+  // environment.
+  bool added_chrome_etw_variable_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileLogger);
+};
+
+#endif  // CHROME_TEST_BASE_FILE_LOGGER_WIN_H_