Create and pass shared-histogram-allocator from browser to renderer.

content/public/test/mock_render_process_host.cc

Index: content/public/test/mock_render_process_host.cc
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 5037893190a68f8ff118e95ee72b7e58a5e7935f..debecdcee32b4015401e5b5e4fba4911bfae42a1 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -263,6 +263,11 @@ ServiceRegistry* MockRenderProcessHost::GetServiceRegistry() {
   return service_registry_.get();
 }
 
+scoped_ptr<base::SharedPersistentMemoryAllocator>
+MockRenderProcessHost::TakeMetricsAllocator() {
+  return nullptr;
+}
+
 const base::TimeTicks& MockRenderProcessHost::GetInitTimeForNavigationMetrics()
     const {
   static base::TimeTicks dummy_time = base::TimeTicks::Now();