service worker: Add trace events for renderer process initialization.

These could be useful to analyze performance, e.g., to see whether
renderer process initialization was slow vs the renderer was too
busy to receive the Start Worker IPC.

Bug: 968424
Change-Id: I46230c92cdc8f28e11730bfc04bdb427a3f35ac5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1636993Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664892}

content/renderer/render_thread_impl.cc

@@ -712,6 +712,7 @@ RenderThreadImpl::RenderThreadImpl(
 
 void RenderThreadImpl::Init() {
   TRACE_EVENT0("startup", "RenderThreadImpl::Init");
+  init_start_ = base::TimeTicks::Now();
 
   GetContentClient()->renderer()->PostIOThreadCreated(GetIOTaskRunner().get());
 
@@ -962,6 +963,8 @@ void RenderThreadImpl::Init() {
     compositing_mode_reporter_->AddCompositingModeWatcher(
         std::move(watcher_ptr));
   }
+
+  init_end_ = base::TimeTicks::Now();
 }
 
 RenderThreadImpl::~RenderThreadImpl() {
@@ -2088,6 +2091,24 @@ void RenderThreadImpl::CreateFrameProxy(
 
 void RenderThreadImpl::SetUpEmbeddedWorkerChannelForServiceWorker(
     blink::mojom::EmbeddedWorkerInstanceClientRequest client_request) {
+  // This is a hack. Process creation and initialization occurs before tracing
+  // is setup, so trace events logged at that time get dropped. We want these
+  // trace events to analyze service worker performance, so log them here.
+  //
+  // TODO(crbug.com/968424): Remove this hack when trace events that happen
+  // early on are supported.
+  if (!init_start_.is_null()) {
+    TRACE_EVENT_BEGIN_WITH_ID_TID_AND_TIMESTAMP0(
+        "ServiceWorker", "RenderThreadImpl initialization", this,
+        0 /* thread_id */, init_start_);
+    TRACE_EVENT_END_WITH_ID_TID_AND_TIMESTAMP0(
+        "ServiceWorker", "RenderThreadImpl initialization", this,
+        0 /* thread_id */, init_end_);
+    // Clear to avoid double logging.
+    init_start_ = base::TimeTicks();
+    init_end_ = base::TimeTicks();
+  }
+
   EmbeddedWorkerInstanceClientImpl::Create(std::move(client_request));
 }
 

content/renderer/render_thread_impl.h

@@ -140,7 +140,7 @@ class StreamTextureFactory;
 #pragma warning(disable: 4250)
 #endif
 
-// The RenderThreadImpl class represents a background thread where RenderView
+// The RenderThreadImpl class represents the main thread, where RenderView
 // instances live.  The RenderThread supports an API that is used by its
 // consumer to talk indirectly to the RenderViews and supporting objects.
 // Likewise, it provides an API for the RenderViews to talk back to the main
@@ -728,6 +728,9 @@ class CONTENT_EXPORT RenderThreadImpl
   mojo::Binding<viz::mojom::CompositingModeWatcher>
       compositing_mode_watcher_binding_;
 
+  base::TimeTicks init_start_;
+  base::TimeTicks init_end_;
+
   base::WeakPtrFactory<RenderThreadImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);