NoStatePrefetch: Remove mojom::PrerenderMode from PrerenderURLLoaderThrottle

PrerenderURLLoaderThrottle::mode_ is always
mojom::PrerenderMode::kPrefetchOnly, so the field is not necessary.

Even after this change, the constructor of PrerenderURLLoaderThrottle
still takes the mode as an argument just for validation check. This will
be removed by follow-up CLs that remove the mode from callers of the
constructor.

Bug: 755921
Change-Id: I72c5cb9ca3c1d03e9316fbf60aa067d3bff02cbc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2592237Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837099}

components/no_state_prefetch/common/prerender_url_loader_throttle.cc

@@ -41,10 +41,11 @@ PrerenderURLLoaderThrottle::PrerenderURLLoaderThrottle(
     prerender::mojom::PrerenderMode mode,
     const std::string& histogram_prefix,
     mojo::PendingRemote<prerender::mojom::PrerenderCanceler> canceler)
-    : mode_(mode),
-      histogram_prefix_(histogram_prefix),
-      canceler_(std::move(canceler)) {
+    : histogram_prefix_(histogram_prefix), canceler_(std::move(canceler)) {
   DCHECK(canceler_);
+  // TODO(https://crbug.com/755921): Remove the `mode` param. This is now kept
+  // just for validation check until mojom::PrerenderMode is completely removed.
+  DCHECK_EQ(mode, mojom::PrerenderMode::kPrefetchOnly);
 }
 
 PrerenderURLLoaderThrottle::~PrerenderURLLoaderThrottle() {
@@ -68,11 +69,9 @@ void PrerenderURLLoaderThrottle::DetachFromCurrentSequence() {
 void PrerenderURLLoaderThrottle::WillStartRequest(
     network::ResourceRequest* request,
     bool* defer) {
-  if (mode_ == prerender::mojom::PrerenderMode::kPrefetchOnly) {
   request->load_flags |= net::LOAD_PREFETCH;
   request->cors_exempt_headers.SetHeader(kPurposeHeaderName,
                                          kPurposeHeaderValue);
-  }
 
   resource_type_ =
       static_cast<blink::mojom::ResourceType>(request->resource_type);
@@ -122,12 +121,10 @@ void PrerenderURLLoaderThrottle::WillStartRequest(
   }
 #endif  // OS_ANDROID
 
-  if (mode_ == prerender::mojom::PrerenderMode::kPrefetchOnly) {
   detached_timer_.Start(FROM_HERE,
                         base::TimeDelta::FromMilliseconds(
                             content::kDefaultDetachableCancelDelayMs),
                         this, &PrerenderURLLoaderThrottle::OnTimedOut);
-  }
 }
 
 void PrerenderURLLoaderThrottle::WillRedirectRequest(
@@ -138,11 +135,9 @@ void PrerenderURLLoaderThrottle::WillRedirectRequest(
     net::HttpRequestHeaders* /* modified_headers */,
     net::HttpRequestHeaders* /* modified_cors_exempt_headers */) {
   redirect_count_++;
-  if (mode_ == prerender::mojom::PrerenderMode::kPrefetchOnly) {
   RecordPrefetchResponseReceived(
       histogram_prefix_, blink::IsResourceTypeFrame(resource_type_),
       true /* is_redirect */, IsNoStoreResponse(response_head));
-  }
 
   std::string follow_only_when_prerender_shown_header;
   if (response_head.headers) {
@@ -167,10 +162,6 @@ void PrerenderURLLoaderThrottle::WillProcessResponse(
     const GURL& response_url,
     network::mojom::URLResponseHead* response_head,
     bool* defer) {
-  if (mode_ != prerender::mojom::PrerenderMode::kPrefetchOnly) {
-    return;
-  }
-
   bool is_main_resource = blink::IsResourceTypeFrame(resource_type_);
   RecordPrefetchResponseReceived(histogram_prefix_, is_main_resource,
                                  true /* is_redirect */,

components/no_state_prefetch/common/prerender_url_loader_throttle.h

@@ -54,7 +54,6 @@ class PrerenderURLLoaderThrottle
 
   void OnTimedOut();
 
-  prerender::mojom::PrerenderMode mode_;
   std::string histogram_prefix_;
 
   bool deferred_ = false;