Reland "Fix form resubmissions happening silently."

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index 80bcdc7c5946f61a057466448b2ee1f4331d9a02..15aad39271f3f6807a74ae1c49a7be776b416a87 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -629,7 +629,7 @@ ResourceRequestCachePolicy ResourceFetcher::resourceRequestCachePolicy(const Res
             return ReturnCacheDataDontLoad;
         if (!m_documentLoader->overrideEncoding().isEmpty() || frameLoadType == FrameLoadTypeBackForward)
             return ReturnCacheDataElseLoad;
-        if (isReload || frameLoadType == FrameLoadTypeSame || request.isConditional())
+        if (isReload || frameLoadType == FrameLoadTypeSame || request.isConditional() || request.httpMethod() == "POST")
             return ReloadIgnoringCacheData;
         return UseProtocolCachePolicy;
     }