DevTools: use explicit IPC messages for enabling/disabling tracing instead of intercepting protocol…

content/common/devtools_messages.h

Index: content/common/devtools_messages.h
diff --git a/content/common/devtools_messages.h b/content/common/devtools_messages.h
index 3e148640d45382101ff5dc2a02471a2f82552d24..151d88f2bb3258666c531d39a3cfb5ba76354916 100644
--- a/content/common/devtools_messages.h
+++ b/content/common/devtools_messages.h
@@ -114,6 +114,13 @@ IPC_MESSAGE_ROUTED1(DevToolsHostMsg_DispatchOnEmbedder,
 IPC_MESSAGE_ROUTED1(DevToolsHostMsg_SaveAgentRuntimeState,
                     std::string /* state */)
 
+// Tells the host to enable trace event recording.
+IPC_MESSAGE_ROUTED1(DevToolsHostMsg_EnableTracing,
+                    std::string /* category_filter */)
+
+// Tells the host to disable trace event recording.
+IPC_MESSAGE_ROUTED0(DevToolsHostMsg_DisableTracing)
+
 //-----------------------------------------------------------------------------
 // These are messages sent from the GPU process to the inspected renderer.