Teach ContentSecurityPolicy about WebURLRequest::RequestContext.

Source/core/html/parser/HTMLResourcePreloader.cpp

Index: Source/core/html/parser/HTMLResourcePreloader.cpp
diff --git a/Source/core/html/parser/HTMLResourcePreloader.cpp b/Source/core/html/parser/HTMLResourcePreloader.cpp
index 3f1ee72eab01460a69638136a0c6c97b2c5eaa87..1b9fbd358c4b0b874f40b0092d54fa2d964ca206 100644
--- a/Source/core/html/parser/HTMLResourcePreloader.cpp
+++ b/Source/core/html/parser/HTMLResourcePreloader.cpp
@@ -32,6 +32,7 @@
 #include "core/html/imports/HTMLImport.h"
 #include "core/rendering/RenderObject.h"
 #include "public/platform/Platform.h"
+#include "public/platform/WebURLRequest.h"
 
 namespace blink {
 
@@ -55,6 +56,7 @@ FetchRequest PreloadRequest::resourceRequest(Document* document)
     initiatorInfo.name = AtomicString(m_initiatorName);
     initiatorInfo.position = m_initiatorPosition;
     FetchRequest request(ResourceRequest(completeURL(document)), initiatorInfo);
+    request.mutableResourceRequest().setRequestContext(blink::WebURLRequest::RequestContextPrefetch);
 
     if (m_isCORSEnabled)
         request.setCrossOriginAccessControl(document->securityOrigin(), m_allowCredentials);