Add trace event for detecting main frame in loading metrics.

third_party/WebKit/Source/web/WebLocalFrameImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1578 matching lines @@
     }
 
     // TODO(dominickn): This interface should be document-scoped rather than
     // frame-scoped, as the resulting banner event is dispatched to
     // frame()->document().
     frame()->interfaceRegistry()->addInterface(WTF::bind(
         &AppBannerController::bindMojoRequest, wrapWeakPersistent(frame())));
 
     frame()->interfaceRegistry()->addInterface(WTF::bind(
         &InstallationServiceImpl::create, wrapWeakPersistent(frame())));
+    if (!owner) {
+      // This trace event is needed to detect the main frame of the
+      // renderer in telemetry metrics. See crbug.com/692112#c11.
+      TRACE_EVENT_INSTANT1("loading", "markAsMainFrame",
+                           TRACE_EVENT_SCOPE_THREAD, "frame", frame());
+    }
   }
 }
 
 LocalFrame* WebLocalFrameImpl::createChildFrame(
     const FrameLoadRequest& request,
     const AtomicString& name,
     HTMLFrameOwnerElement* ownerElement) {
   DCHECK(m_client);
   TRACE_EVENT0("blink", "WebLocalFrameImpl::createChildframe");
   WebTreeScopeType scope = frame()->document() == ownerElement->treeScope()
@@ skipping 829 matching lines @@
         createMarkup(startPosition, endPosition, AnnotateForInterchange,
                      ConvertBlocksToInlines::NotConvert, ResolveNonLocalURLs);
   } else {
     clipHtml =
         createMarkup(endPosition, startPosition, AnnotateForInterchange,
                      ConvertBlocksToInlines::NotConvert, ResolveNonLocalURLs);
   }
 }
 
 }  // namespace blink