Send a scheme of http or https as appropriate, rather than grpc.

This requires additional logic to determine whether to send http or
https. This change assumes a default of http, and plumbs down https
through a synthesized channel arg when using the ssl transport.

src/core/channel/http_client_filter.c

@@ -32,6 +32,7 @@
  */
 
 #include "src/core/channel/http_client_filter.h"
+#include <string.h>
 #include <grpc/support/log.h>
 
 typedef struct call_data { int sent_headers; } call_data;
@@ -130,6 +131,19 @@ static void destroy_call_elem(grpc_call_element *elem) {
   ignore_unused(channeld);
 }
 
+static char *scheme_from_args(const grpc_channel_args *args) {
+  int i;
+  if (args != NULL) {
+    for (i = 0; i < args->num_args; ++i) {
+      if (args->args[i].type == GRPC_ARG_STRING &&
+          strcmp(args->args[i].key, "grpc.scheme") == 0) {
+        return args->args[i].value.string;
+      }
+    }
+  }
+  return "http";
+}
+
 /* Constructor for channel_data */
 static void init_channel_elem(grpc_channel_element *elem,
                               const grpc_channel_args *args, grpc_mdctx *mdctx,
@@ -146,7 +160,8 @@ static void init_channel_elem(grpc_channel_element *elem,
   /* initialize members */
   channeld->te_trailers = grpc_mdelem_from_strings(mdctx, "te", "trailers");
   channeld->method = grpc_mdelem_from_strings(mdctx, ":method", "POST");
-  channeld->scheme = grpc_mdelem_from_strings(mdctx, ":scheme", "grpc");
+  channeld->scheme =
+      grpc_mdelem_from_strings(mdctx, ":scheme", scheme_from_args(args));
   channeld->content_type =
       grpc_mdelem_from_strings(mdctx, "content-type", "application/grpc");
 }

src/core/security/security_context.c

@@ -35,6 +35,7 @@
 
 #include <string.h>
 
+#include "src/core/channel/channel_args.h"
 #include "src/core/security/credentials.h"
 #include "src/core/security/secure_endpoint.h"
 #include "src/core/surface/lame_client.h"
@@ -444,6 +445,8 @@ grpc_channel *grpc_ssl_channel_create(grpc_credentials *ssl_creds,
   grpc_security_status status = GRPC_SECURITY_OK;
   size_t i = 0;
   const char *secure_peer_name = target;
+  grpc_arg arg;
+  grpc_channel_args *new_args;
 
   for (i = 0; args && i < args->num_args; i++) {
     grpc_arg *arg = &args->args[i];
@@ -459,8 +462,13 @@ grpc_channel *grpc_ssl_channel_create(grpc_credentials *ssl_creds,
   if (status != GRPC_SECURITY_OK) {
     return grpc_lame_client_channel_create();
   }
-  channel = grpc_secure_channel_create_internal(target, args, ctx);
+  arg.type = GRPC_ARG_STRING;
+  arg.key = "grpc.scheme";
+  arg.value.string = "https";
+  new_args = grpc_channel_args_copy_and_add(args, &arg);
+  channel = grpc_secure_channel_create_internal(target, new_args, ctx);
   grpc_security_context_unref(&ctx->base);
+  grpc_channel_args_destroy(new_args);
   return channel;
 }