Add RAIL tracing category to Chrome tracing.

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 839 matching lines @@
         return TracedValue::create();
     std::unique_ptr<TracedValue> value = m_analyzer->toTracedValue();
     value->setString("host", layoutViewItem().document().location()->host());
     value->setString("frame", String::format("0x%" PRIxPTR, reinterpret_cast<uintptr_t>(m_frame.get())));
     value->setInteger("contentsHeightAfterLayout", layoutViewItem().documentRect().height());
     value->setInteger("visibleHeight", visibleHeight());
     value->setInteger("approximateBlankCharacterCount", FontFaceSet::approximateBlankCharacterCount(*m_frame->document()));
     return value;
 }
 
-#define PERFORM_LAYOUT_TRACE_CATEGORIES "blink,benchmark," TRACE_DISABLED_BY_DEFAULT("blink.debug.layout")
+#define PERFORM_LAYOUT_TRACE_CATEGORIES "blink,benchmark,rail," TRACE_DISABLED_BY_DEFAULT("blink.debug.layout")
 
 void FrameView::performLayout(bool inSubtreeLayout)
 {
     ASSERT(inSubtreeLayout || m_layoutSubtreeRootList.isEmpty());
 
     TRACE_EVENT_BEGIN1(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout",
         "contentsHeightBeforeLayout", layoutViewItem().documentRect().height());
     prepareLayoutAnalyzer();
 
     ScriptForbiddenScope forbidScript;
@@ skipping 3377 matching lines @@
 }
 
 bool FrameView::canThrottleRendering() const
 {
     if (!RuntimeEnabledFeatures::renderingPipelineThrottlingEnabled())
         return false;
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 } // namespace blink