Add logging for request blocking by the RedirectToFileResourceHandler.

content/browser/loader/redirect_to_file_resource_handler.cc

Index: content/browser/loader/redirect_to_file_resource_handler.cc
diff --git a/content/browser/loader/redirect_to_file_resource_handler.cc b/content/browser/loader/redirect_to_file_resource_handler.cc
index 2d55420e95a9f62ef659daf9e3bb6f8f56a63da6..a30d9dc68e2a3e4363d634b9cd6eff428d7061dd 100644
--- a/content/browser/loader/redirect_to_file_resource_handler.cc
+++ b/content/browser/loader/redirect_to_file_resource_handler.cc
@@ -172,6 +172,7 @@ bool RedirectToFileResourceHandler::OnWillStart(const GURL& url, bool* defer) {
   // network request like this.
   will_start_url_ = url;
   did_defer_ = *defer = true;
+  request()->LogBlockedBy("RedirectToFileResourceHandler");
   if (create_temporary_file_stream_.is_null()) {
     CreateTemporaryFileStream(
         base::Bind(&RedirectToFileResourceHandler::DidCreateTemporaryFile,
@@ -215,6 +216,7 @@ bool RedirectToFileResourceHandler::OnReadCompleted(int bytes_read,
 
   if (BufIsFull()) {
     did_defer_ = *defer = true;
+    request()->LogBlockedBy("RedirectToFileResourceHandler");
 
     if (buf_->capacity() == bytes_read) {
       // The network layer has saturated our buffer in one read. Next time, we
@@ -234,6 +236,7 @@ void RedirectToFileResourceHandler::OnResponseCompleted(
     completed_status_ = status;
     did_defer_ = true;
     *defer = true;
+    request()->LogBlockedBy("RedirectToFileResourceHandler");
     return;
   }
   next_handler_->OnResponseCompleted(status, defer);
@@ -254,10 +257,11 @@ void RedirectToFileResourceHandler::DidCreateTemporaryFile(
   // Resume the request.
   DCHECK(did_defer_);
   bool defer = false;
+  request()->LogUnblocked();
   if (!next_handler_->OnWillStart(will_start_url_, &defer)) {
     controller()->Cancel();
   } else if (!defer) {
-    ResumeIfDeferred();
+    Resume();
   } else {
     did_defer_ = false;
   }
@@ -293,9 +297,10 @@ void RedirectToFileResourceHandler::DidWriteToFile(int result) {
     // this should run even in the |failed| case above, otherwise a failed write
     // leaves the handler stuck.
     bool defer = false;
+    request()->LogUnblocked();
     next_handler_->OnResponseCompleted(completed_status_, &defer);
     if (!defer) {
-      ResumeIfDeferred();
+      Resume();
     } else {
       did_defer_ = false;
     }
@@ -309,8 +314,10 @@ bool RedirectToFileResourceHandler::WriteMore() {
       // We've caught up to the network load, but it may be in the process of
       // appending more data to the buffer.
       if (!buf_write_pending_) {
-        if (BufIsFull())
-          ResumeIfDeferred();
+        if (BufIsFull()) {
+          request()->LogUnblocked();
+          Resume();

[mmenke, 2017/01/06 17:56:17]

Randy:  This looks like a bug to me:

If this is called from OnReadCompleted, and BufIsFull(), we set did_defer_ to
true in OnReadCompleted before calling this method.  Then if we write the entire
buffer synchronously in this loop, we end up here (write_cursor_ ==
buf_->offset(), !buf_write_pending_, BufIsFull() are all true)....And then we
call Resume().  But we haven't yet deferred the request!

Am I missing something?  This issue existed before this CL.

[Randy Smith (Not in Mondays), 2017/01/09 21:55:27]

Nice catch.  This looks like a bug in RTFRH, but not one that is going to be
tripped--at least, it looks to me as if writer_->Write() below will always
return either an error or ERR_IO_PENDING, which means we'll never go around the
loop.   I've filed http://crbug.com/679483 to track it, but I don't think we
need to fix it with high priority (unless I'm missing a synchronous return path
from the called functions).

+        }
         buf_->set_offset(0);
         write_cursor_ = 0;
       }
@@ -356,11 +363,10 @@ bool RedirectToFileResourceHandler::BufIsFull() const {
   return buf_->RemainingCapacity() <= (2 * net::kMaxBytesToSniff);
 }
 
-void RedirectToFileResourceHandler::ResumeIfDeferred() {
-  if (did_defer_) {
-    did_defer_ = false;
-    controller()->Resume();
-  }
+void RedirectToFileResourceHandler::Resume() {
+  DCHECK(did_defer_);
+  did_defer_ = false;
+  controller()->Resume();
 }
 
 }  // namespace content