Check the return value when canceling prerenders.

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h"
 
 #include <string>
 
 #include "base/base64.h"
 #include "base/logging.h"
@@ skipping 210 matching lines @@
       return false;
 
     // If prefetch is disabled, kill the request.
     if (!prerender::PrerenderManager::IsPrefetchEnabled())
       return false;
   }
 
   // Abort any prerenders that spawn requests that use invalid HTTP methods
   // or invalid schemes.
   if (prerender_tracker_->IsPrerenderingOnIOThread(child_id, route_id)) {
-    if (!prerender::PrerenderManager::IsValidHttpMethod(method)) {
-      prerender_tracker_->TryCancelOnIOThread(
-          child_id, route_id, prerender::FINAL_STATUS_INVALID_HTTP_METHOD);
+    if (!prerender::PrerenderManager::IsValidHttpMethod(method) &&
+        prerender_tracker_->TryCancelOnIOThread(
+            child_id, route_id, prerender::FINAL_STATUS_INVALID_HTTP_METHOD)) {
       return false;
     }
-    if (!prerender::PrerenderManager::DoesSubresourceURLHaveValidScheme(url)) {
+    if (!prerender::PrerenderManager::DoesSubresourceURLHaveValidScheme(url) &&
+        prerender_tracker_->TryCancelOnIOThread(
+            child_id, route_id, prerender::FINAL_STATUS_UNSUPPORTED_SCHEME)) {
       ReportUnsupportedPrerenderScheme(url);
-      prerender_tracker_->TryCancelOnIOThread(
-          child_id, route_id, prerender::FINAL_STATUS_UNSUPPORTED_SCHEME);
       return false;
     }
   }
 
   return true;
 }
 
 void ChromeResourceDispatcherHostDelegate::RequestBeginning(
     net::URLRequest* request,
     content::ResourceContext* resource_context,
@@ skipping 168 matching lines @@
 }
 
 bool ChromeResourceDispatcherHostDelegate::HandleExternalProtocol(
     const GURL& url, int child_id, int route_id) {
 #if defined(OS_ANDROID)
   // Android use a resource throttle to handle external as well as internal
   // protocols.
   return false;
 #else
 
-  if (prerender_tracker_->IsPrerenderingOnIOThread(child_id, route_id)) {
+  if (prerender_tracker_->IsPrerenderingOnIOThread(child_id, route_id) &&
+      prerender_tracker_->TryCancel(
+          child_id, route_id, prerender::FINAL_STATUS_UNSUPPORTED_SCHEME)) {
     ReportPrerenderSchemeCancelReason(
         PRERENDER_SCHEME_CANCEL_REASON_EXTERNAL_PROTOCOL);
-    prerender_tracker_->TryCancel(
-        child_id, route_id, prerender::FINAL_STATUS_UNSUPPORTED_SCHEME);
     return false;
   }
 
   ExtensionRendererState::WebViewInfo info;
   if (ExtensionRendererState::GetInstance()->GetWebViewInfo(child_id,
                                                             route_id,
                                                             &info)) {
     return false;
   }
 
@@ skipping 201 matching lines @@
 
   if (io_data->resource_prefetch_predictor_observer()) {
     io_data->resource_prefetch_predictor_observer()->OnRequestRedirected(
         redirect_url, request);
   }
 
   int child_id, route_id;
   if (!prerender::PrerenderManager::DoesURLHaveValidScheme(redirect_url) &&
       ResourceRequestInfo::ForRequest(request)->GetAssociatedRenderView(
           &child_id, &route_id) &&
-      prerender_tracker_->IsPrerenderingOnIOThread(child_id, route_id)) {
+      prerender_tracker_->IsPrerenderingOnIOThread(child_id, route_id) &&
+      prerender_tracker_->TryCancel(
+          child_id, route_id, prerender::FINAL_STATUS_UNSUPPORTED_SCHEME)) {
     ReportUnsupportedPrerenderScheme(redirect_url);
-    prerender_tracker_->TryCancel(
-        child_id, route_id, prerender::FINAL_STATUS_UNSUPPORTED_SCHEME);
     request->Cancel();
   }
 }