Mojo: Refactor URLLoader interface.

mojo/services/public/interfaces/network/url_loader.mojom

Index: mojo/services/public/interfaces/network/url_loader.mojom
diff --git a/mojo/services/public/interfaces/network/url_loader.mojom b/mojo/services/public/interfaces/network/url_loader.mojom
index 22d5fdb5c7a3decf1cf54c96c75a3dd2de82b359..da340c4cf0226b75c0dd095300385c5f2de7f8f5 100644
--- a/mojo/services/public/interfaces/network/url_loader.mojom
+++ b/mojo/services/public/interfaces/network/url_loader.mojom
@@ -16,15 +16,20 @@ struct URLRequest {
   // Additional HTTP request headers.
   string[] headers;
 
-  // The payload for the request body. For HTTP requests, the method must be
-  // set to "POST" or "PUT".
-  handle<data_pipe_consumer> body;
+  // The payload for the request body, represented as a concatenation of data
+  // streams. For HTTP requests, the method must be set to "POST" or "PUT".
+  handle<data_pipe_consumer>[] body;
 
   // The number of bytes to be read from |body|. A Content-Length header of
   // this value will be sent. Set to -1 if length is unknown, which will cause
   // |body| to be uploaded using a chunked encoding.
   int64 body_length = 0;
 
+  // The buffer size of the data pipe returned in URLResponse's |body| member.
+  // A value of 0 indicates that the default buffer size should be used.  This
+  // value is just a suggestion. The URLLoader may choose to ignore this value.
+  uint32 response_body_buffer_size = 0;
+
   // If set to true, then redirects will be automatically followed. Otherwise,
   // when a redirect is encounterd, FollowRedirect must be called to proceed.
   bool auto_follow_redirects = false;
@@ -37,6 +42,13 @@ struct URLRequest {
 };
 
 struct URLResponse {
+  // If the response resulted in a network level error, this field will be set.
+  NetworkError error;
+
+  // The response body stream. Read from this data pipe to receive the bytes of
+  // response body.
+  handle<data_pipe_consumer> body;
+
   // The final URL of the response, after redirects have been followed.
   string url;
 
@@ -54,47 +66,41 @@ struct URLResponse {
 
   // The character set of the response body.
   string charset;
+
+  // These fields are set to non-NULL if this response corresponds to a
+  // redirect.  Call the |FollowRedirect| method on the URLLoader instance to
+  // follow this redirect.
+  string redirect_method;
+  string redirect_url;
+};
+
+struct URLLoaderStatus {
+  // If the loader has failed due to a network level error, this field will be
+  // set.
+  NetworkError error;
+
+  // Set to true if the URLLoader is still working. Set to false once an error
+  // is encountered or the response body is completely copied to the response
+  // body stream.
+  bool is_loading;
+
+  // TODO(darin): Add further details about the stages of loading (e.g.,
+  // "resolving host") that happen prior to receiving bytes.
 };
 
-[Client=URLLoaderClient]
 interface URLLoader {
-  // Start loading the given |request|. When available, the response body will
-  // be copied to |response_body_stream|.
-  //
-  // The client's |OnReceivedResponse| method will run when response meta data
-  // becomes available, or if a redirect response is encountered and
-  // |auto_follow_redirects| is false, the client's |OnRecievedRedirect| method
-  // will called instead.
-  //
-  // NOTE: You may observe data being pushed to |response_body_stream| before
-  // you receive |OnReceivedResponse|.
-  Start(URLRequest request, handle<data_pipe_producer> response_body_stream);
+  // Loads the given |request|, asynchronously producing |response|. Consult
+  // |response| to determine if the request resulted in an error, was
+  // redirected, or has a response body to be consumed.
+  Start(URLRequest request) => (URLResponse response);
 
   // If the request passed to |Start| had |auto_follow_redirects| set to false,
-  // then upon receiving a redirect, |OnReceivedRedirect| will be called. To
-  // follow the indicated redirect, call the |FollowRedirect| method.
-  FollowRedirect();
-};
+  // then upon receiving an URLResponse with a non-NULL |redirect_url| field,
+  // |FollowRedirect| may be called to load the URL indicated by the redirect.
+  FollowRedirect() => (URLResponse response);
 
-interface URLLoaderClient {
-  // This method is called when a redirect is encountered, provided the
-  // request's |auto_follow_redirects| attribute was set to false.
-  OnReceivedRedirect(URLResponse response, string new_url, string new_method);
-
-  // This method is called when response meta data becomes available.
-  OnReceivedResponse(URLResponse response);
-
-  // This method is called when a network level error is encountered. This can
-  // happen before or after OnReceivedResponse, but cannot happen after
-  // OnReceivedEndOfResponseBody.
-  OnReceivedError(NetworkError error);
-
-  // This method is called when the response body has been successfully
-  // downloaded and copied in its entirety to |response_body_stream|.
-  //
-  // NOTE: Because |response_body_stream| is limited in size, this event may be
-  // delayed until |response_body_stream| is consumed.
-  OnReceivedEndOfResponseBody();
+  // Query status about the URLLoader.
+  QueryStatus() => (URLLoaderStatus status);
 };
 
 }