Drop MemoryCache support for non-GET requests

Have Resource::CanReuse return false when the request method is not GET.
This is harmless because currently all the preload requests and requests
that can be served from the MemoryCache are GET requests, given that
RawResources are not served from the MemoryCache.

This change will allow us not to store the request body in Resource,
which will be important when we introduce streaming upload because
we do not want to copy a streaming request body.

Bug: 688906
Change-Id: I5b1b01a6f003378f0ac33f528d209c610178fa29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2024627Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736237}

third_party/blink/renderer/platform/loader/fetch/resource.cc

@@ -823,12 +823,13 @@ Resource::MatchStatus Resource::CanReuse(const FetchParameters& params) const {
   if (resource_request_.GetKeepalive() || new_request.GetKeepalive())
     return MatchStatus::kKeepaliveSet;
 
-  if (GetResourceRequest().HttpMethod() != new_request.HttpMethod())
+  if (GetResourceRequest().HttpMethod() != http_names::kGET ||
+      new_request.HttpMethod() != http_names::kGET) {
     return MatchStatus::kRequestMethodDoesNotMatch;
+  }
 
-  if (GetResourceRequest().HttpBody() != new_request.HttpBody())
-    return MatchStatus::kUnknownFailure;
-
+  // A GET request doesn't have a request body.
+  DCHECK(!new_request.HttpBody());
 
   // Don't reuse an existing resource when the source origin is different.
   if (!existing_origin->IsSameOriginWith(new_origin.get()))

third_party/blink/renderer/platform/loader/fetch/resource_fetcher.cc

@@ -158,24 +158,12 @@ ResourceLoadPriority TypeToPriority(ResourceType type) {
   return ResourceLoadPriority::kUnresolved;
 }
 
-static bool IsCacheableHTTPMethod(const AtomicString& method) {
-  // Per http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.10,
-  // these methods always invalidate the cache entry.
-  return method != http_names::kPOST && method != http_names::kPUT &&
-         method != "DELETE";
-}
-
 bool ShouldResourceBeAddedToMemoryCache(const FetchParameters& params,
                                         Resource* resource) {
-  if (!IsMainThread())
-    return false;
-  if (params.Options().data_buffering_policy == kDoNotBufferData)
-    return false;
-  if (IsRawResource(*resource))
-    return false;
-  if (!IsCacheableHTTPMethod(params.GetResourceRequest().HttpMethod()))
-    return false;
-  return true;
+  return IsMainThread() &&
+         params.GetResourceRequest().HttpMethod() == http_names::kGET &&
+         params.Options().data_buffering_policy != kDoNotBufferData &&
+         !IsRawResource(*resource);
 }
 
 static ResourceFetcher::ResourceFetcherSet& MainThreadFetchersSet() {