[Cronet] Provide shim from deprecated cronet_c_for_grpc API to bidirectional_stream_c API.

components/cronet/ios/Cronet.h

Index: components/cronet/ios/Cronet.h
diff --git a/components/cronet/ios/Cronet.h b/components/cronet/ios/Cronet.h
index fc42612f8b3b8d0576e9af31260f7ac4973367d9..ba3dd7dc13b4858abe0093cd512997ab953f4bb6 100644
--- a/components/cronet/ios/Cronet.h
+++ b/components/cronet/ios/Cronet.h
@@ -6,6 +6,10 @@
 
 #include "bidirectional_stream_c.h"
 
+// TODO(mef): Remove this header after transition to bidirectional_stream_c.h
+// See crbug.com/650462 for details.
+#include "cronet_c_for_grpc.h"
+
 // A block, that takes a request, and returns YES if the request should
 // be handled.
 typedef BOOL (^RequestFilterBlock)(NSURLRequest* request);