Chromium roll (https://codereview.chromium.org/976353002)

base/test/mock_log.cc

Index: base/test/mock_log.cc
diff --git a/base/test/mock_log.cc b/base/test/mock_log.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fa511d44d08645e4f45b8cc33622205239441c1f
--- /dev/null
+++ b/base/test/mock_log.cc
@@ -0,0 +1,68 @@
+// Copyright 2015 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.
+
+#include "base/test/mock_log.h"
+
+namespace base {
+namespace test {
+
+// static
+MockLog* MockLog::g_instance_ = nullptr;
+Lock MockLog::g_lock;
+
+MockLog::MockLog() : is_capturing_logs_(false) {
+}
+
+MockLog::~MockLog() {
+  if (is_capturing_logs_) {
+    StopCapturingLogs();
+  }
+}
+
+void MockLog::StartCapturingLogs() {
+  AutoLock scoped_lock(g_lock);
+
+  // We don't use CHECK(), which can generate a new LOG message, and
+  // thus can confuse MockLog objects or other registered
+  // LogSinks.
+  RAW_CHECK(!is_capturing_logs_);
+  RAW_CHECK(!g_instance_);
+
+  is_capturing_logs_ = true;
+  g_instance_ = this;
+  previous_handler_ = logging::GetLogMessageHandler();
+  logging::SetLogMessageHandler(LogMessageHandler);
+}
+
+void MockLog::StopCapturingLogs() {
+  AutoLock scoped_lock(g_lock);
+
+  // We don't use CHECK(), which can generate a new LOG message, and
+  // thus can confuse MockLog objects or other registered
+  // LogSinks.
+  RAW_CHECK(is_capturing_logs_);
+  RAW_CHECK(g_instance_ == this);
+
+  is_capturing_logs_ = false;
+  logging::SetLogMessageHandler(previous_handler_);
+  g_instance_ = nullptr;
+}
+
+// static
+bool MockLog::LogMessageHandler(int severity,
+                                const char* file,
+                                int line,
+                                size_t message_start,
+                                const std::string& str) {
+  // gMock guarantees thread-safety for calling a mocked method
+  // (https://code.google.com/p/googlemock/wiki/CookBook#Using_Google_Mock_and_Threads)
+  // but we also need to make sure that Start/StopCapturingLogs are synchronized
+  // with LogMessageHandler.
+  AutoLock scoped_lock(g_lock);
+
+  return g_instance_->Log(severity, file, line, message_start, str);
+}
+
+}  // namespace test
+}  // namespace base