NavigationTiming: set navigationStart for navigations in new tabs.

content/renderer/render_frame_impl.cc

 // Copyright 2013 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.
 
 #include "content/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 
 #include "base/auto_reset.h"
@@ skipping 866 matching lines @@
         data = reinterpret_cast<const char*>(
             &params.browser_initiated_post_data.front());
       }
       http_body.appendData(
           WebData(data, params.browser_initiated_post_data.size()));
       request.setHTTPBody(http_body);
     }
 
     frame->loadRequest(request);
 
-    // If this is a cross-process navigation, the browser process will send
-    // along the proper navigation start value.
-    if (!params.browser_navigation_start.is_null() &&
-        frame->provisionalDataSource()) {
+    // The browser provides the navigation_start time to bootstrap the
+    // Navigation Timing information for the browser-initiated navigations. In
+    // case of cross-process navigations, this carries over the time of
+    // finishing the onbeforeunload handler of the previous page.
+    DCHECK(!params.browser_navigation_start.is_null());
+    if (frame->provisionalDataSource()) {
       // browser_navigation_start is likely before this process existed, so we
       // can't use InterProcessTimeTicksConverter. Instead, the best we can do
       // is just ensure we don't report a bogus value in the future.
       base::TimeTicks navigation_start = std::min(
           base::TimeTicks::Now(), params.browser_navigation_start);
       double navigation_start_seconds =
           (navigation_start - base::TimeTicks()).InSecondsF();
       frame->provisionalDataSource()->setNavigationStartTime(
           navigation_start_seconds);
     }
@@ skipping 2663 matching lines @@
 
 #if defined(ENABLE_BROWSER_CDMS)
 RendererCdmManager* RenderFrameImpl::GetCdmManager() {
   if (!cdm_manager_)
     cdm_manager_ = new RendererCdmManager(this);
   return cdm_manager_;
 }
 #endif  // defined(ENABLE_BROWSER_CDMS)
 
 }  // namespace content