Add RAIL tracing category to Chrome tracing.

third_party/WebKit/Source/core/animation/Animation.cpp

Index: third_party/WebKit/Source/core/animation/Animation.cpp
diff --git a/third_party/WebKit/Source/core/animation/Animation.cpp b/third_party/WebKit/Source/core/animation/Animation.cpp
index 6fe5a0f1997df8e6a5b63fdd546263ac260e07dc..02b960277d60ad2c86e590239ea34a3032d1c769 100644
--- a/third_party/WebKit/Source/core/animation/Animation.cpp
+++ b/third_party/WebKit/Source/core/animation/Animation.cpp
@@ -991,11 +991,11 @@ Animation::PlayStateUpdateScope::~PlayStateUpdateScope()
         bool wasActive = oldPlayState == Pending || oldPlayState == Running;
         bool isActive = newPlayState == Pending || newPlayState == Running;
         if (!wasActive && isActive)
-            TRACE_EVENT_NESTABLE_ASYNC_BEGIN1("blink.animations,devtools.timeline,benchmark", "Animation", m_animation, "data", InspectorAnimationEvent::data(*m_animation));
+            TRACE_EVENT_NESTABLE_ASYNC_BEGIN1("blink.animations,devtools.timeline,benchmark,rail", "Animation", m_animation, "data", InspectorAnimationEvent::data(*m_animation));
         else if (wasActive && !isActive)
-            TRACE_EVENT_NESTABLE_ASYNC_END1("blink.animations,devtools.timeline,benchmark", "Animation", m_animation, "endData", InspectorAnimationStateEvent::data(*m_animation));
+            TRACE_EVENT_NESTABLE_ASYNC_END1("blink.animations,devtools.timeline,benchmark,rail", "Animation", m_animation, "endData", InspectorAnimationStateEvent::data(*m_animation));
         else
-            TRACE_EVENT_NESTABLE_ASYNC_INSTANT1("blink.animations,devtools.timeline,benchmark", "Animation", m_animation, "data", InspectorAnimationStateEvent::data(*m_animation));
+            TRACE_EVENT_NESTABLE_ASYNC_INSTANT1("blink.animations,devtools.timeline,benchmark,rail", "Animation", m_animation, "data", InspectorAnimationStateEvent::data(*m_animation));
     }
 
     // Ordering is important, the ready promise should resolve/reject before