Revert https://codereview.chromium.org/1291903002 (protobuf roll).

third_party/protobuf/javanano/src/test/java/com/google/protobuf/nano/unittest_extension_nano.proto

Index: third_party/protobuf/javanano/src/test/java/com/google/protobuf/nano/unittest_extension_nano.proto
diff --git a/third_party/protobuf/javanano/src/test/java/com/google/protobuf/nano/unittest_extension_nano.proto b/third_party/protobuf/javanano/src/test/java/com/google/protobuf/nano/unittest_extension_nano.proto
deleted file mode 100644
index ca56b3dd45477af1cde0e5b143cfa8532807cdf6..0000000000000000000000000000000000000000
--- a/third_party/protobuf/javanano/src/test/java/com/google/protobuf/nano/unittest_extension_nano.proto
+++ /dev/null
@@ -1,37 +0,0 @@
-syntax = "proto2";
-
-option java_outer_classname = "Extensions";
-option java_package = "com.google.protobuf.nano.testext";
-
-message ExtendableMessage {
-  optional int32 field = 1;
-  extensions 10 to max;
-}
-
-enum AnEnum {
-  FIRST_VALUE = 1;
-  SECOND_VALUE = 2;
-}
-
-message AnotherMessage {
-  optional string string = 1;
-  optional bool value = 2;
-  repeated int32 integers = 3;
-}
-
-message ContainerMessage {
-  extend ExtendableMessage {
-    optional bool another_thing = 100;
-    // The largest permitted field number, per
-    // https://developers.google.com/protocol-buffers/docs/proto#simple
-    optional bool large_field_number = 536870911;
-  }
-}
-
-// For testNanoOptionalGroupWithUnknownFieldsEnabled;
-// not part of the extensions tests.
-message MessageWithGroup {
-  optional group Group = 1 {
-    optional int32 a = 2;
-  }
-}