Implement about:tracing UI for the sampling profiler (Chromium part)

base/debug/trace_event.h

Index: base/debug/trace_event.h
diff --git a/base/debug/trace_event.h b/base/debug/trace_event.h
index 43eb09c4771318528290d38d1ab0b28565da0833..7d00be84d7cb3f7f4752b45f36d816b59ed93a81 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -928,7 +928,9 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
 #define TRACE_EVENT_FLAG_COPY         (static_cast<unsigned char>(1 << 0))
 #define TRACE_EVENT_FLAG_HAS_ID       (static_cast<unsigned char>(1 << 1))
 #define TRACE_EVENT_FLAG_MANGLE_ID    (static_cast<unsigned char>(1 << 2))
-#define TRACE_EVENT_FLAG_SCOPE_OFFSET (static_cast<unsigned char>(1 << 3))
+#define TRACE_EVENT_FLAG_CONTINUOUS_SAMPLING \
+    (static_cast<unsigned char>(1 << 3))
+#define TRACE_EVENT_FLAG_SCOPE_OFFSET (static_cast<unsigned char>(1 << 4))
 
 #define TRACE_EVENT_FLAG_SCOPE_MASK   (static_cast<unsigned char>( \
     TRACE_EVENT_FLAG_SCOPE_OFFSET | (TRACE_EVENT_FLAG_SCOPE_OFFSET << 1)))
@@ -945,9 +947,9 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
 
 // Enum reflecting the scope of an INSTANT event. Must fit within
 // TRACE_EVENT_FLAG_SCOPE_MASK.
-#define TRACE_EVENT_SCOPE_GLOBAL  (static_cast<unsigned char>(0 << 3))
-#define TRACE_EVENT_SCOPE_PROCESS (static_cast<unsigned char>(1 << 3))
-#define TRACE_EVENT_SCOPE_THREAD  (static_cast<unsigned char>(2 << 3))
+#define TRACE_EVENT_SCOPE_GLOBAL  (static_cast<unsigned char>(0 << 4))
+#define TRACE_EVENT_SCOPE_PROCESS (static_cast<unsigned char>(1 << 4))
+#define TRACE_EVENT_SCOPE_THREAD  (static_cast<unsigned char>(2 << 4))
 
 #define TRACE_EVENT_SCOPE_NAME_GLOBAL  ('g')
 #define TRACE_EVENT_SCOPE_NAME_PROCESS ('p')