Moving gRPC support interfaces out of cronet and into a new component.

components/cronet/ios/test/start_cronet.h

Index: components/cronet/ios/test/start_cronet.h
diff --git a/components/tracing/test/example_proto/upper_import.proto b/components/cronet/ios/test/start_cronet.h
similarity index 57%
copy from components/tracing/test/example_proto/upper_import.proto
copy to components/cronet/ios/test/start_cronet.h
index c948d2e8b1f52b0da523b83acb5fbfd45544c3ea..9216eb5f1845578829240313dad89336acb6a3e5 100644
--- a/components/tracing/test/example_proto/upper_import.proto
+++ b/components/cronet/ios/test/start_cronet.h
@@ -2,10 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-syntax = "proto2";
-option optimize_for = LITE_RUNTIME;
+namespace cronet {
 
-package foo.bar;
+// Starts Cronet if it hasn't already been started.
+void StartCronetIfNecessary();
 
-message TrickyPublicImport {
-}
+}  // namespace cronet