Avoid double download for late discovered link preload resources.

third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp

Index: third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
diff --git a/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp b/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
index 58f0257ec8445b61639a30252021a7619c303f01..d800f84503b84e2158fcf8f32c448024dc40dc79 100644
--- a/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
+++ b/third_party/WebKit/Source/core/fetch/ResourceFetcher.cpp
@@ -829,7 +829,7 @@ bool ResourceFetcher::isPreloaded(const KURL& url) const
     return false;
 }
 
-void ResourceFetcher::clearPreloads()
+void ResourceFetcher::clearPreloads(ClearPreloadsType type)
 {
 #if PRELOAD_DEBUG
     printPreloadStats();
@@ -840,7 +840,7 @@ void ResourceFetcher::clearPreloads()
     for (auto resource : *m_preloads) {
         resource->decreasePreloadCount();
         bool deleted = resource->deleteIfPossible();
-        if (!deleted && resource->preloadResult() == Resource::PreloadNotReferenced)
+        if (!deleted && resource->preloadResult() == Resource::PreloadNotReferenced && (type == ClearAllPreloads || !resource->avoidBlockingOnLoad()))

[Nate Chapin, 2016/01/21 19:07:14]

I assume avoidBlockingOnLoad() is checked because that will only be set in the
rel=preload case? Maybe add a comment to explain that?

[Yoav Weiss, 2016/01/21 20:34:09]

added

             memoryCache()->remove(resource.get());
     }
     m_preloads.clear();