Add load flag indicating a request is probably the result of a user gesture.

content/browser/renderer_host/resource_dispatcher_host.cc

Index: content/browser/renderer_host/resource_dispatcher_host.cc
diff --git a/content/browser/renderer_host/resource_dispatcher_host.cc b/content/browser/renderer_host/resource_dispatcher_host.cc
index 24ef6825bfd520b7177f8b5f97cb61a6294aaa40..8e9f1323ab624a6cd5b4cb1e7930116c5ff66f1b 100644
--- a/content/browser/renderer_host/resource_dispatcher_host.cc
+++ b/content/browser/renderer_host/resource_dispatcher_host.cc
@@ -18,7 +18,6 @@
 #include "base/metrics/histogram.h"
 #include "base/shared_memory.h"
 #include "base/stl_util.h"
-#include "base/time.h"
 #include "chrome/browser/download/download_file_manager.h"
 #include "chrome/browser/download/download_manager.h"
 #include "chrome/browser/download/download_request_limiter.h"
@@ -116,6 +115,14 @@ const int kMaxPendingDataMessages = 20;
 // This bound is 25MB, which allows for around 6000 outstanding requests.
 const int kMaxOutstandingRequestsCostPerProcess = 26214400;
 
+// The number of milliseconds after noting a user gesture that we will
+// tag newly-created URLRequest objects with the
+// net::LOAD_MAYBE_USER_GESTURE load flag. This is a fairly arbitrary
+// guess at how long to expect direct impact from a user gesture, but
+// this should be OK as the load flag is a best-effort thing only,
+// rather than being intended as fully accurate.
+const int kUserGestureWindowMs = 3500;
+
 // All possible error codes from the network module. Note that the error codes
 // are all positive (since histograms expect positive sample values).
 const int kAllNetErrorCodes[] = {
@@ -1409,6 +1416,12 @@ void ResourceDispatcherHost::BeginRequestInternal(net::URLRequest* request) {
   DCHECK(!request->is_pending());
   ResourceDispatcherHostRequestInfo* info = InfoForRequest(request);
 
+  if ((TimeTicks::Now() - last_user_gesture_time_) <
+      TimeDelta::FromMilliseconds(kUserGestureWindowMs)) {
+    request->set_load_flags(
+        request->load_flags() | net::LOAD_MAYBE_USER_GESTURE);
+  }
+
   // Add the memory estimate that starting this request will consume.
   info->set_memory_cost(CalculateApproximateMemoryCost(request));
   int memory_cost = IncrementOutstandingRequestsMemoryCost(info->memory_cost(),
@@ -1674,6 +1687,12 @@ void ResourceDispatcherHost::OnResponseCompleted(net::URLRequest* request) {
   // call until later.  We will notify the world and clean up when we resume.
 }
 
+void ResourceDispatcherHost::OnUserGesture(TabContents* tab) {
+  download_request_limiter()->OnUserGesture(tab);
+
+  last_user_gesture_time_ = TimeTicks::Now();
+}
+
 // static
 ResourceDispatcherHostRequestInfo* ResourceDispatcherHost::InfoForRequest(
     net::URLRequest* request) {