Dispatch transfer size update notification on mojo-loading

content/common/url_loader.mojom

Index: content/common/url_loader.mojom
diff --git a/content/common/url_loader.mojom b/content/common/url_loader.mojom
index f77988b238bd2d74a1d6a29e8b682de11ce9bec8..4e92378ac41818a649cae703feb802d1aae752dc 100644
--- a/content/common/url_loader.mojom
+++ b/content/common/url_loader.mojom
@@ -44,8 +44,20 @@ interface URLLoaderClient {
   // Called when some data from a resource request has been downloaded to the
   // file. This is only called in the 'download_to_file' case and replaces
   // OnStartLoadingResponseBody in the call sequence in that case.
+  // TODO(yhirano): Remove |encoded_length| and use OnTransferSizeUpdated
+  // instead.
   OnDataDownloaded(int64 data_length, int64 encoded_length);
 
+  // Called when the transfer size is updated. This is only called if
+  // |report_raw_headers| is set and |download_to_file| is unset in the request.
+  // The transfer size is the length of the response (including both headers
+  // and the body) over the network. |transfer_size_diff| is the difference from
+  // the value previously reported one (including the one in OnReceiveResponse
+  // and OnReceiveRedirect). It must be positive.

[dcheng, 2016/12/15 06:29:02]

Nit: usually we use unsigned to express that "it must be positive". I guess that
would be a lot of trouble to change now... but it might be worth fixing
eventually?

[yhirano, 2016/12/15 11:28:00]

Google c++ style guide says 

"
You should not use the unsigned integer types such as uint32_t, unless there is
a valid reason such as representing a bit pattern rather than a number, or you
need defined overflow modulo 2^N. In particular, do not use unsigned types to
say a number will never be negative. Instead, use assertions for this.
"

https://google.github.io/styleguide/cppguide.html#Integer_Types

so I am using signed int.

[dcheng, 2016/12/15 16:23:59]

google style really dislikes unsigned. However, for IPC, we do explicitly
recommend using unsigned:
https://www.chromium.org/Home/chromium-security/education/security-tips-for-i....

I think it's OK to add a TODO for that (since that matches legacy ipc). However,
for the integer size issue, is it OK to just use int32 for now? We can change
this to int64 if/when we decide to change the integer types throughout the rest
of the system.

[yhirano, 2016/12/16 05:30:23]

Done.

+  // TODO(yhirano): Dispatch this notification even when |download_to_file| is
+  // set.
+  OnTransferSizeUpdated(int64 transfer_size_diff);
+
   // Called when the loader starts loading response body.
   OnStartLoadingResponseBody(handle<data_pipe_consumer> body);