Add support for single sample metrics.

components/test/run_all_unittests.cc

Index: components/test/run_all_unittests.cc
diff --git a/components/test/run_all_unittests.cc b/components/test/run_all_unittests.cc
index 92af0b5ffee37d0d66d431ae29cddb4111456a9d..4e449338548529cc310a7e24448af4f5d1a1258b 100644
--- a/components/test/run_all_unittests.cc
+++ b/components/test/run_all_unittests.cc
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 #include "components/test/components_test_suite.h"
+#include "mojo/edk/embedder/embedder.h"
 
 int main(int argc, char** argv) {
+  mojo::edk::Init();
   return base::LaunchUnitTests(argc, argv, GetLaunchCallback(argc, argv));
 }