New test infrastructure for producing verbose logs in failing tests.

chrome/test/logging/win/file_logger.h

Index: chrome/test/logging/win/file_logger.h
diff --git a/chrome/test/logging/win/file_logger.h b/chrome/test/logging/win/file_logger.h
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+// 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_LOGGING_WIN_FILE_LOGGER_H_
+#define CHROME_TEST_LOGGING_WIN_FILE_LOGGER_H_
+#pragma once
+
+#include <guiddef.h>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/string16.h"
+#include "base/win/event_trace_controller.h"
+
+class FilePath;
+
+namespace logging_win {
+
+// A file logger instance captures LOG messages and trace events emitted via
+// Event Tracing for Windows (ETW) and sends them to a file.  Events can be
+// pulled from the file sometime later with PrintLogFile or ReadLogFile
+// (currently in log_file_printer_win.h and log_file_reader_win.h,
+// respectively).
+//
+// Important usage notes (read this):
+// - Due to the nature of event generation, only one instance of this class may
+//   be initialized at a time.
+// - 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);
+
+  // 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) or if no providers could be
+  // enabled.
+  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:
+  // A helper for setting/clearing a variable in the system-wide environment.
+  class ScopedSystemEnvironmentVariable {
+   public:
+    ScopedSystemEnvironmentVariable(const string16& variable,
+                                    const string16& value);
+    ~ScopedSystemEnvironmentVariable();
+
+   private:
+    static void NotifyOtherProcesses();
+
+    // Non-empty if the variable was inserted into the system-wide environment.
+    string16 variable_;
+    DISALLOW_COPY_AND_ASSIGN(ScopedSystemEnvironmentVariable);
+  };
+
+  bool EnableProviders();
+  void DisableProviders();
+
+  void ConfigureChromeEtwLogging();
+  void RevertChromeEtwLogging();
+
+  static bool is_initialized_;
+
+  scoped_ptr<ScopedSystemEnvironmentVariable> etw_logging_configurator_;
+  base::win::EtwTraceController controller_;
+  uint32 event_provider_mask_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileLogger);
+};
+
+}  // namespace logging_win
+
+#endif  // CHROME_TEST_LOGGING_WIN_FILE_LOGGER_H_