service worker: Add temporary instrumentation to debug startup failures.

Somehow service workers are timing out and I don't see what could have
changed. We are timing out in "Allocate Process" before a Start mesage
is sent to the renderer, which suggests some thread on the brower
process is hung somewhere. Try to get more info by generating a crash
report which will also let us see if any unusual command line flags
or features are enabled.

Bug: 843456
Change-Id: Ia4f8d8506e02ef0f0166530172ef033c300a1494
Reviewed-on: https://chromium-review.googlesource.com/1063571Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559447}

content/browser/service_worker/service_worker_version.cc

@@ -11,6 +11,7 @@
 #include <string>
 
 #include "base/command_line.h"
+#include "base/debug/dump_without_crashing.h"
 #include "base/guid.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
@@ -1792,6 +1793,15 @@ void ServiceWorkerVersion::RecordStartWorkerResult(
   UMA_HISTOGRAM_ENUMERATION("ServiceWorker.StartWorker.TimeoutPhase",
                             phase,
                             EmbeddedWorkerInstance::STARTING_PHASE_MAX_VALUE);
+
+  if (IsInstalled(prestart_status) && !s_dumped_for_timeout_) {
+    // TODO(crbug.com/843456): Remove this instrumentation when the linked bug
+    // is fixed.
+    s_dumped_for_timeout_ = true;
+    DEBUG_ALIAS_FOR_GURL(script_url, script_url_);
+    base::debug::Alias(&phase);
+    base::debug::DumpWithoutCrashing();
+  }
 }
 
 bool ServiceWorkerVersion::MaybeTimeoutRequest(
@@ -2015,4 +2025,7 @@ bool ServiceWorkerVersion::IsStartWorkerAllowed() const {
   return true;
 }
 
+// static
+bool ServiceWorkerVersion::s_dumped_for_timeout_ = false;
+
 }  // namespace content

content/browser/service_worker/service_worker_version.h

@@ -864,6 +864,8 @@ class CONTENT_EXPORT ServiceWorkerVersion
 
   base::WeakPtrFactory<ServiceWorkerVersion> weak_factory_;
 
+  static bool s_dumped_for_timeout_;
+
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerVersion);
 };