[instrumentation] Generalize instrumentation to be used beyond the core layer

third_party/WebKit/Source/platform/loader/fetch/FetchContext.cpp

 /*
  * Copyright (C) 2013 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 12 matching lines @@
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "platform/loader/fetch/FetchContext.h"
 
+#include "platform/PlatformInstrumentationAgents.h"
+#include "platform/instrumentation/PlatformTraceEventsAgent.h"
 #include "public/platform/WebCachePolicy.h"
 
 namespace blink {
 
 FetchContext& FetchContext::nullInstance() {
   DEFINE_STATIC_LOCAL(FetchContext, instance, (new FetchContext));
   return instance;
 }
 
+FetchContext::FetchContext()
+    : m_instrumentingAgents(new PlatformInstrumentationAgents) {
+  m_instrumentingAgents->addPlatformTraceEventsAgent(
+      new PlatformTraceEventsAgent);
+}
+
+DEFINE_TRACE(FetchContext) {
+  visitor->trace(m_instrumentingAgents);
+}
+
 void FetchContext::dispatchDidChangeResourcePriority(unsigned long,
                                                      ResourceLoadPriority,
                                                      int) {}
 
 void FetchContext::addAdditionalRequestHeaders(ResourceRequest&,
                                                FetchResourceType) {}
 
 CachePolicy FetchContext::getCachePolicy() const {
   return CachePolicyVerify;
 }
@@ skipping 55 matching lines @@
                                      FetchContext::LogMessageType) const {}
 
 void FetchContext::populateResourceRequest(Resource::Type,
                                            const ClientHintsPreferences&,
                                            const FetchRequest::ResourceWidth&,
                                            ResourceRequest&) {}
 
 void FetchContext::setFirstPartyCookieAndRequestorOrigin(ResourceRequest&) {}
 
 }  // namespace blink