Send an event to the page load metrics to track resource starting.

chrome/browser/page_load_metrics/page_load_metrics_observer.h

Index: chrome/browser/page_load_metrics/page_load_metrics_observer.h
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_observer.h b/chrome/browser/page_load_metrics/page_load_metrics_observer.h
index 11a98896bd91bf72d28f0f68b05251f2ef5229f3..347cbc767f175eeeb37a069a41b0f13250b4dd07 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_observer.h
+++ b/chrome/browser/page_load_metrics/page_load_metrics_observer.h
@@ -196,15 +196,16 @@ struct PageLoadExtraInfo {
 };
 
 // Container for various information about a request within a page load.
-struct ExtraRequestInfo {
-  ExtraRequestInfo(bool was_cached,
-                   int64_t raw_body_bytes,
-                   bool data_reduction_proxy_used,
-                   int64_t original_network_content_length);
+struct ExtraRequestCompleteInfo {
+  ExtraRequestCompleteInfo(bool was_cached,
+                           int64_t raw_body_bytes,
+                           bool data_reduction_proxy_used,
+                           int64_t original_network_content_length,
+                           content::ResourceType found_type);
 
-  ExtraRequestInfo(const ExtraRequestInfo& other);
+  ExtraRequestCompleteInfo(const ExtraRequestCompleteInfo& other);
 
-  ~ExtraRequestInfo();
+  ~ExtraRequestCompleteInfo();
 
   // True if the resource was loaded from cache.
   const bool was_cached;
@@ -218,6 +219,23 @@ struct ExtraRequestInfo {
   // The number of body (not header) bytes that the data reduction proxy saw
   // before it compressed the requests.
   const int64_t original_network_content_length;
+
+  // The type of the request as gleaned from the
+  // ChromeResourceDispatcherHostDelegate.

[RyanSturm, 2017/04/14 20:08:43]

I'd adjust this comment to say "from ResourceRequestInfo" if you want to specify
the source of the value. Same below.

[Pete Williamson, 2017/04/17 18:53:11]

Done in both places.

+  const content::ResourceType resource_type;
+};
+
+// Container for various information about a request within a page load.
+struct ExtraRequestStartInfo {
+  explicit ExtraRequestStartInfo(content::ResourceType type);
+
+  ExtraRequestStartInfo(const ExtraRequestStartInfo& other);
+
+  ~ExtraRequestStartInfo();
+
+  // The type of the request as gleaned from the
+  // ChromeResourceDispatcherHostDelegate.
+  const content::ResourceType resource_type;
 };
 
 // Interface for PageLoadMetrics observers. All instances of this class are
@@ -375,8 +393,13 @@ class PageLoadMetricsObserver {
       const FailedProvisionalLoadInfo& failed_provisional_load_info,
       const PageLoadExtraInfo& extra_info) {}
 
+  // Called whenever a request load begins.
+  virtual void OnStartedResource(
+      const ExtraRequestStartInfo& extra_request_start_info) {}
+
   // Called whenever a request is loaded for this page load.
-  virtual void OnLoadedResource(const ExtraRequestInfo& extra_request_info) {}
+  virtual void OnLoadedResource(
+      const ExtraRequestCompleteInfo& extra_request_complete_info) {}
 };
 
 }  // namespace page_load_metrics