Added basic client hints support.

Source/core/fetch/ResourceFetcher.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
@@ skipping 28 matching lines @@
 #include "core/fetch/ImageResource.h"
 #include "core/fetch/MemoryCache.h"
 #include "core/fetch/RawResource.h"
 #include "core/fetch/ResourceLoader.h"
 #include "core/fetch/ResourceLoaderSet.h"
 #include "core/fetch/ScriptResource.h"
 #include "core/fetch/SubstituteData.h"
 #include "core/fetch/UniqueIdentifier.h"
 #include "core/fetch/XSLStyleSheetResource.h"
 #include "core/frame/FrameHost.h"
+#include "core/frame/FrameView.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/html/HTMLElement.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/html/imports/HTMLImportsController.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/loader/DocumentLoader.h"
@@ skipping 654 matching lines @@
     m_validatedURLs.add(request.resourceRequest().url());
 }
 
 ResourcePtr<Resource> ResourceFetcher::requestResource(Resource::Type type, FetchRequest& request)
 {
     ASSERT(request.options().synchronousPolicy == RequestAsynchronously || type == Resource::Raw);
 
     TRACE_EVENT0("blink", "ResourceFetcher::requestResource");
 
     upgradeInsecureRequest(request);
+    addClientHintsIfNeccessary(request);
 
     KURL url = request.resourceRequest().url();
 
     WTF_LOG(ResourceLoading, "ResourceFetcher::requestResource '%s', charset '%s', priority=%d, forPreload=%u, type=%s", url.elidedString().latin1().data(), request.charset().latin1().data(), request.priority(), request.forPreload(), ResourceTypeName(type));
 
     // If only the fragment identifiers differ, it is the same resource.
     url = MemoryCache::removeFragmentIdentifierIfNeeded(url);
 
     if (!url.isValid())
         return nullptr;
@@ skipping 193 matching lines @@
             || url.host() == m_document->securityOrigin()->host())
         {
             url.setProtocol("https");
             if (url.port() == 80)
                 url.setPort(443);
             fetchRequest.mutableResourceRequest().setURL(url);
         }
     }
 }
 
+void ResourceFetcher::addClientHintsIfNeccessary(FetchRequest& fetchRequest)
+{
+    if (!RuntimeEnabledFeatures::clientHintsEnabled() || !m_document || !frame())
+        return;
+
+    if (frame()->shouldSendDPRHint())
+        fetchRequest.mutableResourceRequest().addHTTPHeaderField("DPR", AtomicString(String::number(m_document->devicePixelRatio())));
+
+    // FIXME: Send the RW hint based on the actual resource width, when we have it.
+    if (frame()->shouldSendRWHint() && frame()->view())
+        fetchRequest.mutableResourceRequest().addHTTPHeaderField("RW", AtomicString(String::number(frame()->view()->viewportWidth())));
+}
+
 ResourcePtr<Resource> ResourceFetcher::createResourceForRevalidation(const FetchRequest& request, Resource* resource)
 {
     ASSERT(resource);
     ASSERT(memoryCache()->contains(resource));
     ASSERT(resource->isLoaded());
     ASSERT(resource->canUseCacheValidator());
     ASSERT(!resource->resourceToRevalidate());
     ASSERT(!isControlledByServiceWorker());
 
     ResourceRequest revalidatingRequest(resource->resourceRequest());
@@ skipping 706 matching lines @@
     ResourceLoaderHost::trace(visitor);
 }
 
 ResourceFetcher* ResourceFetcher::toResourceFetcher(ResourceLoaderHost* host)
 {
     ASSERT(host->objectType() == ResourceLoaderHost::ResourceFetcherType);
     return static_cast<ResourceFetcher*>(host);
 }
 
 }