Make reprioritization IPC batch rather than per-request.

content/browser/loader/resource_scheduler.h

Index: content/browser/loader/resource_scheduler.h
diff --git a/content/browser/loader/resource_scheduler.h b/content/browser/loader/resource_scheduler.h
index 76b455c409fd5cd87f3764b72dce42d7f48abf6d..53c8c4614a842e4559878d64e5ae4dc48d7c68b8 100644
--- a/content/browser/loader/resource_scheduler.h
+++ b/content/browser/loader/resource_scheduler.h
@@ -54,6 +54,12 @@ class ResourceThrottle;
 // the URLRequest.
 class CONTENT_EXPORT ResourceScheduler : public base::NonThreadSafe {
  public:
+  struct PriorityChangeRequest {
+    net::URLRequest* request;
+    net::RequestPriority priority;
+    int intra_priority;
+  };
+
   ResourceScheduler();
   ~ResourceScheduler();
 
@@ -103,6 +109,11 @@ class CONTENT_EXPORT ResourceScheduler : public base::NonThreadSafe {
                            net::RequestPriority new_priority,
                            int intra_priority_value);
 
+  // Update the priority for a set of requests.  Modifies request->priority()
+  // and may start the request loading if it wasn't already started.
+  void ReprioritizeRequests(
+      const std::vector<PriorityChangeRequest>& change_requests);
+
  private:
   // Returns the maximum number of delayable requests to all be in-flight at
   // any point in time (across all hosts).