Add support for single sample metrics.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index bd4ef1a6c6400f651419daaff4a67dff50dc3957..4b7fe4c78e4b52236550e5900b289a8c0ca16c10 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -51,6 +51,8 @@
 #include "cc/trees/layer_tree_host_common.h"
 #include "cc/trees/layer_tree_settings.h"
 #include "components/discardable_memory/client/client_discardable_shared_memory_manager.h"
+#include "components/metrics/public/interfaces/single_value_histograms.mojom.h"
+#include "components/metrics/single_value_histograms_factory_impl.h"
 #include "content/child/appcache/appcache_dispatcher.h"
 #include "content/child/appcache/appcache_frontend_impl.h"
 #include "content/child/blob_storage/blob_message_filter.h"
@@ -608,6 +610,16 @@ void RenderThreadImpl::Init(
   // Register this object as the main thread.
   ChildProcess::current()->set_main_thread(this);
 
+  // In single process mode we may already have a factory set.
+  if (!base::SingleValueHistogramsFactory::Get()) {
+    metrics::mojom::SingleValueHistogramsProviderPtr metric_provider;
+    GetConnector()->BindInterface(mojom::kBrowserServiceName,
+                                  mojo::MakeRequest(&metric_provider));
+    base::SingleValueHistogramsFactory::SetFactory(
+        new metrics::SingleValueHistogramsFactoryImpl(
+            base::ThreadTaskRunnerHandle::Get(), std::move(metric_provider)));
+  }
+
   gpu_ = ui::Gpu::Create(
       GetConnector(),
       IsRunningInMash() ? ui::mojom::kServiceName : mojom::kBrowserServiceName,