Revert of [Prerender] Restore request priorities when swapped in

chrome/browser/prerender/prerender_resource_throttle.cc

Index: chrome/browser/prerender/prerender_resource_throttle.cc
diff --git a/chrome/browser/prerender/prerender_resource_throttle.cc b/chrome/browser/prerender/prerender_resource_throttle.cc
index b6ed41fdabf0878b3bce20130d8cb5f42a0cec50..afd908fe6db2c2b387927c3fea5619109a906278 100644
--- a/chrome/browser/prerender/prerender_resource_throttle.cc
+++ b/chrome/browser/prerender/prerender_resource_throttle.cc
@@ -12,7 +12,6 @@
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_util.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/resource_dispatcher_host.h"
 #include "content/public/browser/web_contents.h"
 #include "net/base/load_flags.h"
 #include "net/http/http_response_headers.h"
@@ -86,29 +85,7 @@
 PrerenderResourceThrottle::PrerenderResourceThrottle(net::URLRequest* request)
     : request_(request),
       load_flags_(net::LOAD_NORMAL),
-      prerender_throttle_info_(new PrerenderThrottleInfo()) {
-// Priorities for prerendering requests are lowered, to avoid competing with
-// other page loads, except on Android where this is less likely to be a
-// problem. In some cases, this may negatively impact the performance of
-// prerendering, see https://crbug.com/652746 for details.
-#if !defined(OS_ANDROID)
-  // Requests with the IGNORE_LIMITS flag set (i.e., sync XHRs)
-  // should remain at MAXIMUM_PRIORITY.
-  if (request_->load_flags() & net::LOAD_IGNORE_LIMITS) {
-    DCHECK_EQ(request_->priority(), net::MAXIMUM_PRIORITY);
-  } else if (request_->priority() != net::IDLE) {
-    original_request_priority_ = request_->priority();
-    // In practice, the resource scheduler does not know about the request yet,
-    // and it falls back to calling request_->SetPriority(), so it would be
-    // possible to do just that here. It is cleaner and more robust to go
-    // through the resource dispatcher host though.
-    if (content::ResourceDispatcherHost::Get()) {
-      content::ResourceDispatcherHost::Get()->ReprioritizeRequest(request_,
-                                                                  net::IDLE);
-    }
-  }
-#endif  // OS_ANDROID
-}
+      prerender_throttle_info_(new PrerenderThrottleInfo()) {}
 
 PrerenderResourceThrottle::~PrerenderResourceThrottle() {}
 
@@ -117,7 +94,6 @@
   const content::ResourceRequestInfo* info =
       content::ResourceRequestInfo::ForRequest(request_);
   *defer = true;
-
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&PrerenderResourceThrottle::WillStartRequestOnUI, AsWeakPtr(),
@@ -171,16 +147,6 @@
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   request_->SetLoadFlags(request_->load_flags() | load_flags_);
   Resume();
-}
-
-void PrerenderResourceThrottle::ResetResourcePriority() {
-  if (!original_request_priority_)
-    return;
-
-  if (content::ResourceDispatcherHost::Get()) {
-    content::ResourceDispatcherHost::Get()->ReprioritizeRequest(
-        request_, original_request_priority_.value());
-  }
 }
 
 // static
@@ -236,16 +202,9 @@
       // Delay icon fetching until the contents are getting swapped in
       // to conserve network usage in mobile devices.
       prerender_contents->AddResourceThrottle(throttle);
-
-      // No need to call AddIdleResource() on Android.
       return;
 #endif
     }
-
-#if !defined(OS_ANDROID)
-    if (!cancel)
-      prerender_contents->AddIdleResource(throttle);
-#endif
   }
 
   BrowserThread::PostTask(