New test infrastructure for producing verbose logs in failing tests.

chrome/test/base/file_logger_win.h

Index: chrome/test/base/file_logger_win.h
diff --git a/chrome/test/base/file_logger_win.h b/chrome/test/base/file_logger_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..97b1c3f95021743d12de2b836a6f3b3f3ab461f6
--- /dev/null
+++ b/chrome/test/base/file_logger_win.h
@@ -0,0 +1,77 @@
+// 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 <ostream>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/win/event_trace_controller.h"
+
+class FilePath;
+
+// A file logger instance captures LOG messages emitted as events 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.  Due to the nature of
+// event generation, only one instance of this class may be initialized at a
+// time.

[robertshield, 2012/03/02 22:37:41]

Consider adding a note here that this requires admin privileges and not to call
it if writing a test that runs without them.

[grt (UTC plus 2), 2012/03/03 02:12:43]

Done.

+class FileLogger {
+ public:
+  FileLogger();
+  ~FileLogger();
+
+  // Initializes the instance to collect logs from the default set of providers:
+  // - chrome.exe
+  // - npchrome_frame.dll
+  // - this test binary.
+  // The system-wide variable CHROME_ETW_LOGGING=1 is added to the environment
+  // if it is not present.

[robertshield, 2012/03/02 22:37:41]

* The variable CHROME_ETW_LOGGING=1 is added to the system-wide environment if
it is not present.

[grt (UTC plus 2), 2012/03/03 02:12:43]

Done.

+  void Initialize();
+
+  // Initializes the instance to collect logs from the given providers.
+  void Initialize(const GUID* const* provider_names, size_t provider_count);
+
+  // 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.
+  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();
+  }
+
+  // Dumps all messages in |log_file|, which must have been produced by an
+  // instance of this class, to |out|.
+  static void DumpLogFile(const FilePath& log_file, std::ostream& out);
+
+ private:
+  bool EnableProviders();
+  void DisableProviders();
+
+  void ConfigureChromeEtwLogging();
+  void RevertChromeEtwLogging();
+
+  std::vector<GUID> provider_names_;
+  base::win::EtwTraceController controller_;
+
+  // 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_