Use a monotonic clock (TimeTicks) to report network times to WebCore.

content/common/resource_messages.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // IPC messages for resource loading.
 
 // Multiply-included message file, hence no include guard.
 #include "base/shared_memory.h"
 #include "content/common/resource_response.h"
 #include "ipc/ipc_message_macros.h"
@@ skipping 129 matching lines @@
 // ResourceMsg_DataReceived in the call sequence in that case.
 IPC_MESSAGE_ROUTED2(ResourceMsg_DataDownloaded,
                     int /* request_id */,
                     int /* data_len */)
 
 // Sent when the request has been completed.
 IPC_MESSAGE_ROUTED4(ResourceMsg_RequestComplete,
                     int /* request_id */,
                     net::URLRequestStatus /* status */,
                     std::string /* security info */,
-                    base::Time /* completion_time */)
+                    base::TimeTicks /* completion_time */)

[darin (slow to review), 2011/08/29 23:42:56]

Are you sure it makes sense to send TimeTicks over IPC?  Do all processes really
have the same tick source?

[James Simonsen, 2011/08/30 00:09:31]

Yep. This has been a popular question in this code review. :)

All the platforms implement this with some sort of "system time" that's
implemented in the kernel and accessed with a system call. They all count time
since the OS booted.

Here are the some of my sources for each platform:

timeGetTime() - http://msdn.microsoft.com/en-us/library/dd743637(v=VS.85).aspx

clock_gettime() -
http://stackoverflow.com/questions/4943733/is-clock-monotonic-process-or-thre...

mach_absolute_time() -
http://google.com/codesearch#pFm0LxzAWvs/darwinsource/tarballs/apsl/xnu-792.t...

There is one discrepancy across platforms wrt suspending the machine. Mac and
Linux stop ticking while suspended. Windows continues to tick. We should
probably figure out how to normalize that across platforms, but it doesn't
actually interfere with anything here.

 
 // Resource messages sent from the renderer to the browser.
 
 // Makes a resource request via the browser.
 IPC_MESSAGE_ROUTED2(ResourceHostMsg_RequestResource,
                     int /* request_id */,
                     ResourceHostMsg_Request)
 
 // Cancels a resource request with the ID given as the parameter.
 IPC_MESSAGE_ROUTED1(ResourceHostMsg_CancelRequest,
@@ skipping 29 matching lines @@
                     int /* request_id */)
 
 // Sent by the renderer process to acknowledge receipt of a
 // UploadProgress message.
 IPC_MESSAGE_ROUTED1(ResourceHostMsg_UploadProgress_ACK,
                     int /* request_id */)
 
 // Sent when the renderer process deletes a resource loader.
 IPC_MESSAGE_CONTROL1(ResourceHostMsg_ReleaseDownloadedFile,
                      int /* request_id */)