Add a runtime flag in WebRuntimeFeatures to enable 'image/webp' accept header

Source/WebCore/loader/cache/CachedImage.cpp

Index: Source/WebCore/loader/cache/CachedImage.cpp
diff --git a/Source/WebCore/loader/cache/CachedImage.cpp b/Source/WebCore/loader/cache/CachedImage.cpp
index 1ca2dfccc79cb693bf3af14def5b108f9c86dc35..78cf0ee386fb3dd01ce03484bfacd423f59fcdfc 100644
--- a/Source/WebCore/loader/cache/CachedImage.cpp
+++ b/Source/WebCore/loader/cache/CachedImage.cpp
@@ -48,6 +48,10 @@
 #include "SVGImage.h"
 #endif
 
+#if USE(WEBP)
+#include "RuntimeEnabledFeatures.h"
+#endif
+
 using std::max;
 
 namespace WebCore {
@@ -58,6 +62,7 @@ CachedImage::CachedImage(const ResourceRequest& resourceRequest)
     , m_shouldPaintBrokenImage(true)
 {
     setStatus(Unknown);
+    setCustomAcceptHeader();
 }
 
 CachedImage::CachedImage(Image* image)
@@ -67,6 +72,7 @@ CachedImage::CachedImage(Image* image)
 {
     setStatus(Cached);
     setLoading(false);
+    setCustomAcceptHeader();
 }
 
 CachedImage::~CachedImage()
@@ -304,6 +310,14 @@ void CachedImage::clear()
     setEncodedSize(0);
 }
 
+void CachedImage::setCustomAcceptHeader()
+{
+#if USE(WEBP)
+    if (RuntimeEnabledFeatures::webPInAcceptHeaderEnabled())
+        setAccept("image/webp,*/*;q=0.8");
+#endif
+}
+
 inline void CachedImage::createImage()
 {
     // Create the image if it doesn't yet exist.