Split requestResource into request preparation and loading

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

Index: third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
diff --git a/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp b/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
index 3dca6d80058321a5f2fec128765abdcdbe449aa3..b324e6321baa1ee304bb179c0427c7dae13cd83f 100644
--- a/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
+++ b/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
@@ -453,16 +453,13 @@ void ResourceFetcher::updateMemoryCacheStats(Resource* resource,
   }
 }
 
-Resource* ResourceFetcher::requestResource(
-    FetchRequest& request,
-    const ResourceFactory& factory,
-    const SubstituteData& substituteData) {
+bool ResourceFetcher::prepareRequest(FetchRequest& request,
+                                     const ResourceFactory& factory,
+                                     const SubstituteData& substituteData,
+                                     unsigned long identifier,
+                                     Resource*& resource) {

[Nate Chapin, 2017/01/31 19:40:22]

"Resource*&" is dubious. Maybe return an enum:

enum class PrepareRequestPolicy {
  Abort,
  Continue,
  Block
};

...and call resourceForBlockedRequest() is Block is returned?

   ResourceRequest& resourceRequest = request.mutableResourceRequest();
 
-  unsigned long identifier = createUniqueIdentifier();
-  network_instrumentation::ScopedResourceLoadTracker scopedResourceLoadTracker(
-      identifier, resourceRequest);
-  SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.Fetch.RequestResourceTime");
   DCHECK(request.options().synchronousPolicy == RequestAsynchronously ||
          factory.type() == Resource::Raw ||
          factory.type() == Resource::XSLStyleSheet);
@@ -471,12 +468,8 @@ Resource* ResourceFetcher::requestResource(
       factory.type(), request.clientHintsPreferences(),
       request.getResourceWidth(), resourceRequest);
 
-  // TODO(dproy): Remove this. http://crbug.com/659666
-  TRACE_EVENT1("blink", "ResourceFetcher::requestResource", "url",
-               urlForTraceEvent(request.url()));
-
   if (!request.url().isValid())
-    return nullptr;
+    return false;
 
   resourceRequest.setPriority(computeLoadPriority(
       factory.type(), request.resourceRequest(), ResourcePriority::NotVisible,
@@ -491,18 +484,41 @@ Resource* ResourceFetcher::requestResource(
       request.options(), request.forPreload(), request.getOriginRestriction());
   if (blockedReason != ResourceRequestBlockedReason::None) {
     DCHECK(!substituteData.forceSynchronousLoad());
-    return resourceForBlockedRequest(request, factory, blockedReason);
+    resource = resourceForBlockedRequest(request, factory, blockedReason);
+    return false;
   }
 
   context().willStartLoadingResource(
       identifier, resourceRequest, factory.type(),
       request.options().initiatorInfo.name, request.forPreload());
   if (!request.url().isValid())
-    return nullptr;
+    return false;
+
+  resourceRequest.setAllowStoredCredentials(
+      request.options().allowCredentials == AllowStoredCredentials);
+  return true;
+}
+
+Resource* ResourceFetcher::requestResource(
+    FetchRequest& request,
+    const ResourceFactory& factory,
+    const SubstituteData& substituteData) {
+  unsigned long identifier = createUniqueIdentifier();
+  ResourceRequest& resourceRequest = request.mutableResourceRequest();
+  network_instrumentation::ScopedResourceLoadTracker scopedResourceLoadTracker(
+      identifier, resourceRequest);
+  SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.Fetch.RequestResourceTime");
+  // TODO(dproy): Remove this. http://crbug.com/659666
+  TRACE_EVENT1("blink", "ResourceFetcher::requestResource", "url",
+               urlForTraceEvent(request.url()));
+
+  Resource* resource = nullptr;
+
+  if (!prepareRequest(request, factory, substituteData, identifier, resource))
+    return resource;
 
   bool isDataUrl = resourceRequest.url().protocolIsData();
   bool isStaticData = isDataUrl || substituteData.isValid() || m_archive;
-  Resource* resource(nullptr);
   if (isStaticData) {
     resource = resourceForStaticData(request, factory, substituteData);
     // Abort the request if the archive doesn't contain the resource, except in
@@ -528,9 +544,6 @@ Resource* ResourceFetcher::requestResource(
 
   updateMemoryCacheStats(resource, policy, request, factory, isStaticData);
 
-  resourceRequest.setAllowStoredCredentials(
-      request.options().allowCredentials == AllowStoredCredentials);
-
   switch (policy) {
     case Reload:
       memoryCache()->remove(resource);