Disable tracing for profiling service.

Chrome suffers a significant performance degradation when both tracing and
out-of-process heap-profiling are enabled. This is because the profiling service
emits multiple trace events each time it reads from a profiling pipe, which
happens around every 30 allocations or so. For more details, see the thread
https://groups.google.com/a/google.com/forum/#!topic/chrome-benchmarking/rjNyxf_53lU.

Bug: 769583
Change-Id: Iba006679154037268bb91b5baf09857a73aae8d2
Reviewed-on: https://chromium-review.googlesource.com/723747
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510265}

content/child/child_thread_impl.cc

@@ -76,6 +76,7 @@
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/service_manager/public/cpp/interface_provider.h"
 #include "services/service_manager/runner/common/client_util.h"
+#include "services/service_manager/sandbox/sandbox_type.h"
 
 #if defined(OS_POSIX)
 #include "base/posix/global_descriptors.h"
@@ -505,15 +506,11 @@ void ChildThreadImpl::Init(const Options& options) {
   channel_->AddFilter(notification_dispatcher_->GetFilter());
   channel_->AddFilter(service_worker_message_filter_->GetFilter());
 
-  if (!IsInBrowserProcess()) {
-    // In single process mode, browser-side tracing and memory will cover the
-    // whole process including renderers.
-    channel_->AddFilter(new tracing::ChildTraceMessageFilter(
-        ChildProcess::current()->io_task_runner()));
-
-    chrome_trace_event_agent_ =
-        base::MakeUnique<tracing::ChromeTraceEventAgent>(GetConnector());
+  InitTracing();
 
+  // In single process mode, browser-side tracing and memory will cover the
+  // whole process including renderers.
+  if (!IsInBrowserProcess()) {
     if (service_manager_connection_) {
       std::string process_type_str =
           base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
@@ -609,6 +606,28 @@ void ChildThreadImpl::Init(const Options& options) {
 #endif
 }
 
+void ChildThreadImpl::InitTracing() {
+  // In single process mode, browser-side tracing and memory will cover the
+  // whole process including renderers.
+  if (IsInBrowserProcess())
+    return;
+
+  // Tracing adds too much overhead to the profiling service. The only
+  // way to determine if this is the profiling service is by checking the
+  // sandbox type.
+  service_manager::SandboxType sandbox_type =
+      service_manager::SandboxTypeFromCommandLine(
+          *base::CommandLine::ForCurrentProcess());
+  if (sandbox_type == service_manager::SANDBOX_TYPE_PROFILING)
+    return;
+
+  channel_->AddFilter(new tracing::ChildTraceMessageFilter(
+      ChildProcess::current()->io_task_runner()));
+
+  chrome_trace_event_agent_ =
+      base::MakeUnique<tracing::ChromeTraceEventAgent>(GetConnector());
+}
+
 ChildThreadImpl::~ChildThreadImpl() {
 #if BUILDFLAG(IPC_MESSAGE_LOG_ENABLED)
   IPC::Logging::GetInstance()->SetIPCSender(NULL);

content/child/child_thread_impl.h

@@ -213,6 +213,9 @@ class CONTENT_EXPORT ChildThreadImpl
 
   void Init(const Options& options);
 
+  // Sets chrome_trace_event_agent_ if necessary.
+  void InitTracing();
+
   // We create the channel first without connecting it so we can add filters
   // prior to any messages being received, then connect it afterwards.
   void ConnectChannel(mojo::edk::IncomingBrokerClientInvitation* invitation);