Avoid issuing a Read() after draining a request.

A URLRequest can signal the end of a stream by calling OnReadCompleted()
with a byte count of zero. No further reads should be issued after this.
However, ResourceLoader could issue a second Read() if the
ResourceHandler::OnReadCompleted() handler sets defer to true. I.e.

When a read completes:
  URLRequest calls
    -> ResourceLoader::OnReadCompleted(request, 0)
    -> ResourceHandler::OnReadCompleted(id, 0, &defer)
       (ResourceHandler sets defer to true)

Prior to this CL, the behavior on resumption was:

  ResourceHandler calls
    -> ResourceLoader::Resume()
    -> ResourceLoader::ResumeReading()
    -> ResourceLoader::StartReading()
    -> ResourceLoader::ReadMore()
    -> URLRequest::Read()

The new behavior is:

  ResourceHandler calls
    -> ResourceLoader::Resume()
    -> ResourceLoader::ResponseCompleted()

The new behavior is parallel to what happens if the ResourceHandler
didn't defer.

BUG=320394

Review URL: https://codereview.chromium.org/267563004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269518 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 2 insertions, 1 deletions

diff --git a/content/browser/loader/resource_handler.h b/content/browser/loader/resource_handler.h
index 0b942bb..ded3a35 100644
--- a/content/browser/loader/resource_handler.h
+++ b/content/browser/loader/resource_handler.h
@@ -97,7 +97,8 @@ class CONTENT_EXPORT ResourceHandler
   // Data (*bytes_read bytes) was written into the buffer provided by
   // OnWillRead.  A return value of false cancels the request, true continues
   // reading data.  Set |*defer| to true to defer reading more response data.
-  // Call controller()->Resume() to continue reading response data.
+  // Call controller()->Resume() to continue reading response data.  A zero
+  // |bytes_read| signals that no further data is available.
   virtual bool OnReadCompleted(int request_id, int bytes_read,
                                bool* defer) = 0;