Slow Reports - Add message filter to trigger background traces from child processes.

content/browser/tracing/trace_message_filter.cc

Index: content/browser/tracing/trace_message_filter.cc
diff --git a/content/browser/tracing/trace_message_filter.cc b/content/browser/tracing/trace_message_filter.cc
index f981e9d76d2cd778b73b305fbdca68598806a15e..bfee96c4056354aea4fe4c704cfe37bef68beae4 100644
--- a/content/browser/tracing/trace_message_filter.cc
+++ b/content/browser/tracing/trace_message_filter.cc
@@ -5,6 +5,7 @@
 #include "content/browser/tracing/trace_message_filter.h"
 
 #include "components/tracing/tracing_messages.h"
+#include "content/browser/tracing/background_tracing_manager_impl.h"
 #include "content/browser/tracing/tracing_controller_impl.h"
 
 namespace content {
@@ -58,6 +59,8 @@ bool TraceMessageFilter::OnMessageReceived(const IPC::Message& message) {
                         OnGlobalMemoryDumpRequest)
     IPC_MESSAGE_HANDLER(TracingHostMsg_ProcessMemoryDumpResponse,
                         OnProcessMemoryDumpResponse)
+    IPC_MESSAGE_HANDLER(TracingHostMsg_TriggerBackgroundTrace,
+                        OnTriggerBackgroundTrace)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -202,4 +205,8 @@ void TraceMessageFilter::OnProcessMemoryDumpResponse(uint64 dump_guid,
       this, dump_guid, success);
 }
 
+void TraceMessageFilter::OnTriggerBackgroundTrace(const std::string& name) {
+  BackgroundTracingManagerImpl::GetInstance()->OnHistogramTrigger(name);
+}
+
 }  // namespace content