Remove requirement that mojo::Environment be instantiated.

mojo/public/cpp/bindings/tests/binding_callback_unittest.cc

Index: mojo/public/cpp/bindings/tests/binding_callback_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/binding_callback_unittest.cc b/mojo/public/cpp/bindings/tests/binding_callback_unittest.cc
index 2d57683726ab67d46c6d87c750eb54f50462b154..44a8150acf80e182a6ce84d3e519b4e7919e451d 100644
--- a/mojo/public/cpp/bindings/tests/binding_callback_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/binding_callback_unittest.cc
@@ -6,7 +6,6 @@
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
 #include "mojo/public/cpp/bindings/string.h"
-#include "mojo/public/cpp/environment/environment.h"
 #include "mojo/public/cpp/system/message_pipe.h"
 #include "mojo/public/cpp/utility/run_loop.h"
 #include "mojo/public/interfaces/bindings/tests/sample_interfaces.mojom.h"
@@ -120,7 +119,6 @@ class BindingCallbackTest : public testing::Test {
   void PumpMessages() { loop_.RunUntilIdle(); }
 
  private:
-  Environment env_;
   RunLoop loop_;
 };