Control ES2015 'Tail call elimination' language feature via finch flag.

content/test/test_blink_web_unit_test_support.cc

Index: content/test/test_blink_web_unit_test_support.cc
diff --git a/content/test/test_blink_web_unit_test_support.cc b/content/test/test_blink_web_unit_test_support.cc
index 3e7b27ce41548b08739c302e6be59df489851ba7..58cfe76e885e05274c5143d8cb3b25133caa9806 100644
--- a/content/test/test_blink_web_unit_test_support.cc
+++ b/content/test/test_blink_web_unit_test_support.cc
@@ -4,6 +4,7 @@
 
 #include "content/test/test_blink_web_unit_test_support.h"
 
+#include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
@@ -99,6 +100,9 @@ TestBlinkWebUnitTestSupport::TestBlinkWebUnitTestSupport() {
   gin::V8Initializer::LoadV8Snapshot();
   gin::V8Initializer::LoadV8Natives();
 #endif
+  // Set up a FeatureList instance, so that code using that API will not hit
+  // an error that it's not set. Cleared by ClearInstanceForTesting() below.
+  base::FeatureList::SetInstance(make_scoped_ptr(new base::FeatureList));
 
   scoped_refptr<base::SingleThreadTaskRunner> dummy_task_runner;
   scoped_ptr<base::ThreadTaskRunnerHandle> dummy_task_runner_handle;
@@ -157,6 +161,9 @@ TestBlinkWebUnitTestSupport::~TestBlinkWebUnitTestSupport() {
   if (renderer_scheduler_)
     renderer_scheduler_->Shutdown();
   blink::shutdown();
+
+  // Clear the FeatureList that was registered above.
+  base::FeatureList::ClearInstanceForTesting();
 }
 
 blink::WebBlobRegistry* TestBlinkWebUnitTestSupport::blobRegistry() {