Restore ScopedLogger and add documentation.

third_party/WebKit/Source/wtf/AssertionsTest.cpp

+// 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 "wtf/Assertions.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "wtf/text/StringBuilder.h"
+#include <stdio.h>
+
+#if !LOG_DISABLED
+namespace WTF {
+
+static const int kPrinterBufferSize = 256;
+static char gBuffer[kPrinterBufferSize];
+static StringBuilder gBuilder;
+
+static void vprint(const char* format, va_list args)
+{
+    int written = vsnprintf(gBuffer, kPrinterBufferSize, format, args);
+    if (written > 0 && written < kPrinterBufferSize)
+        gBuilder.append(gBuffer);
+}
+
+TEST(AssertionsTest, ScopedLogger)
+{
+    ScopedLogger::setPrintFuncForTests(vprint);
+    {
+        WTF_CREATE_SCOPED_LOGGER(a, "a1");
+        {
+            WTF_CREATE_SCOPED_LOGGER_IF(b, false, "b1");
+            {
+                WTF_CREATE_SCOPED_LOGGER(c, "c");
+                {
+                    WTF_CREATE_SCOPED_LOGGER(d, "d %d %s", -1, "hello");
+                }
+            }
+            WTF_APPEND_SCOPED_LOGGER(b, "b2");
+        }
+        WTF_APPEND_SCOPED_LOGGER(a, "a2 %.1f", 0.5);
+    }
+
+    EXPECT_EQ(
+        "( a1\n"
+        "  ( c\n"
+        "    ( d -1 hello )\n"
+        "  )\n"
+        "  a2 0.5\n"
+        ")\n", gBuilder.toString());
+};
+
+} // namespace WTF
+#endif // !LOG_DISABLED