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

components/tracing/tracing_messages.h

Index: components/tracing/tracing_messages.h
diff --git a/components/tracing/tracing_messages.h b/components/tracing/tracing_messages.h
index 9beb7e1ec37a2b71eb9019be5b04aff9f9902b6e..ed251110c6cc1a89cab27e6a17806b87831efb43 100644
--- a/components/tracing/tracing_messages.h
+++ b/components/tracing/tracing_messages.h
@@ -24,6 +24,16 @@ IPC_MESSAGE_CONTROL3(TracingMsg_BeginTracing,
 // Sent to all child processes to disable trace event recording.
 IPC_MESSAGE_CONTROL0(TracingMsg_EndTracing)
 
+// Sent to all child processes to start continuous sampling tracing.
+IPC_MESSAGE_CONTROL1(TracingMsg_BeginContinuousSamplingTracing,
+                     base::TimeTicks /* browser_time */)
+
+// Sent to all child processes to stop continuous sampling tracing.
+IPC_MESSAGE_CONTROL0(TracingMsg_EndContinuousSamplingTracing)
+
+// Sent to all child processes to dump a result of continuous sampling tracing.
+IPC_MESSAGE_CONTROL0(TracingMsg_ShowContinuousSamplingTracing)
+
 // Sent to all child processes to get trace buffer fullness.
 IPC_MESSAGE_CONTROL0(TracingMsg_GetTraceBufferPercentFull)
 
@@ -38,10 +48,13 @@ IPC_MESSAGE_CONTROL0(TracingMsg_CancelWatchEvent)
 // Notify the browser that this child process supports tracing.
 IPC_MESSAGE_CONTROL0(TracingHostMsg_ChildSupportsTracing)
 
-// Reply from child processes acking ChildProcessMsg_TraceChangeStatus(false).
+// Reply from child processes acking TracingMsg_EndTracing.
 IPC_MESSAGE_CONTROL1(TracingHostMsg_EndTracingAck,
                      std::vector<std::string> /* known_categories */)
 
+// Reply from child processes acking TracingMsg_ShowContinuousSamplingTracing.
+IPC_MESSAGE_CONTROL0(TracingHostMsg_ShowContinuousSamplingTracingAck)
+
 // Sent if the trace buffer becomes full.
 IPC_MESSAGE_CONTROL1(TracingHostMsg_TraceNotification,
                      int /* base::debug::TraceLog::Notification */)
@@ -50,6 +63,11 @@ IPC_MESSAGE_CONTROL1(TracingHostMsg_TraceNotification,
 IPC_MESSAGE_CONTROL1(TracingHostMsg_TraceDataCollected,
                      std::string /*json trace data*/)
 
+// Child processes send trace data of continuous sampling tracing back
+// in JSON chunks.
+IPC_MESSAGE_CONTROL1(TracingHostMsg_ContinuousSamplingTraceDataCollected,
+                     std::string /*json trace data*/)
+
 // Reply to TracingMsg_GetTraceBufferPercentFull.
 IPC_MESSAGE_CONTROL1(TracingHostMsg_TraceBufferPercentFullReply,
                      float /*trace buffer percent full*/)