Restore ScopedLogger and add documentation.

third_party/WebKit/Source/wtf/Assertions.cpp

Index: third_party/WebKit/Source/wtf/Assertions.cpp
diff --git a/third_party/WebKit/Source/wtf/Assertions.cpp b/third_party/WebKit/Source/wtf/Assertions.cpp
index 3829cb304745c443ae4860ecf42266a0af71b6b9..d5c4de4e370359c6acc0f28983ac7d6c86c28331 100644
--- a/third_party/WebKit/Source/wtf/Assertions.cpp
+++ b/third_party/WebKit/Source/wtf/Assertions.cpp
@@ -231,6 +231,101 @@ FrameToNameScope::~FrameToNameScope()
 
 } // anonymous namespace
 
+#if !LOG_DISABLED
+namespace WTF {
+
+ScopedLogger::ScopedLogger(bool condition, const char* format, ...)
+    : m_parent(condition ? current() : 0)
+    , m_multiline(false)
+{
+    if (!condition)
+        return;
+
+    va_list args;
+    va_start(args, format);
+    init(format, args);
+    va_end(args);
+}
+
+ScopedLogger::~ScopedLogger()
+{
+    if (current() == this) {
+        if (m_multiline)
+            indent();
+        else
+            print(" ");
+        print(")\n");
+        current() = m_parent;
+    }
+}
+
+void ScopedLogger::init(const char* format, va_list args)
+{
+    current() = this;
+    if (m_parent)
+        m_parent->writeNewlineIfNeeded();
+    indent();
+    print("( ");
+    m_printFunc(format, args);
+}
+
+void ScopedLogger::writeNewlineIfNeeded()
+{
+    if (!m_multiline) {
+        print("\n");
+        m_multiline = true;
+    }
+}
+
+void ScopedLogger::indent()
+{
+    if (m_parent) {
+        m_parent->indent();
+        printIndent();
+    }
+}
+
+void ScopedLogger::log(const char* format, ...)
+{
+    if (current() != this)
+        return;
+
+    va_list args;
+    va_start(args, format);
+
+    writeNewlineIfNeeded();
+    indent();
+    printIndent();
+    m_printFunc(format, args);
+    print("\n");
+
+    va_end(args);
+}
+
+void ScopedLogger::print(const char* format, ...)
+{
+    va_list args;
+    va_start(args, format);
+    m_printFunc(format, args);
+    va_end(args);
+}
+
+void ScopedLogger::printIndent()
+{
+    print("  ");
+}
+
+ScopedLogger*& ScopedLogger::current()
+{
+    DEFINE_THREAD_SAFE_STATIC_LOCAL(ThreadSpecific<ScopedLogger*>, ref, new ThreadSpecific<ScopedLogger*>);
+    return *ref;
+}
+
+ScopedLogger::PrintFunctionPtr ScopedLogger::m_printFunc = vprintf_stderr_common;
+
+} // namespace WTF
+#endif // !LOG_DISABLED
+
 void WTFPrintBacktrace(void** stack, int size)
 {
     for (int i = 0; i < size; ++i) {