Add page load abort metrics to PageLoadMetrics system

components/page_load_metrics/browser/metrics_web_contents_observer.h

Index: components/page_load_metrics/browser/metrics_web_contents_observer.h
diff --git a/components/page_load_metrics/browser/metrics_web_contents_observer.h b/components/page_load_metrics/browser/metrics_web_contents_observer.h
index 45780c10314b8299d30896b9c7e4127739fec65b..c271f6afd0d4b8af4384e62c9e5f0ece7ee0266c 100644
--- a/components/page_load_metrics/browser/metrics_web_contents_observer.h
+++ b/components/page_load_metrics/browser/metrics_web_contents_observer.h
@@ -12,6 +12,7 @@
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
+#include "net/base/net_errors.h"
 
 namespace content {
 class NavigationHandle;
@@ -24,6 +25,32 @@ class Message;
 
 namespace page_load_metrics {
 
+enum PageLoadEvent {
+  PAGE_LOAD_STARTED,
+
+  // A provisional load is a load before it commits.

[Randy Smith (Not in Mondays), 2015/10/01 17:18:08]

Define commits?  I.e. (assuming I have the right definition) " ... before it
commits (i.e. before the first byte of data is received)."

[Charlie Harrison, 2015/10/01 17:58:17]

Done.

+  // A load failed before it was committed for any reason, e.g. from a user
+  // abort or a network timeout.
+  PAGE_LOAD_FAILED_PROVISIONAL,

[Randy Smith (Not in Mondays), 2015/10/01 17:18:08]

suggestion: I think "FAILED_BEFORE_COMMIT" would be clearer than
"FAILED_PROVISIONAL"?

[Charlie Harrison, 2015/10/01 17:58:17]

Done.

+
+  // A subset of PAGE_LOAD_FAILED_PROVISIONAL, this counts the specific failures
+  // due to user aborts.
+  PAGE_LOAD_ABORTED_PROVISIONAL,
+
+  // When a load is aborted anytime before the page's first layout, we increase
+  // this count. This includes all failed provisional loads.
+  PAGE_LOAD_ABORTED_BEFORE_FIRST_LAYOUT,
+
+  // We increase this count if a page load successfully has a layout.

[Randy Smith (Not in Mondays), 2015/10/01 17:18:09]

nit: "these counts"

[Charlie Harrison, 2015/10/01 17:58:17]

Done.

+  // Differentiate between loads that were backgrounded before first layout.

[Randy Smith (Not in Mondays), 2015/10/01 17:18:08]

Just confirming: If a page is backgrounded and then foregrounded before first
layout, it'll still go in the BG bucket?

[Charlie Harrison, 2015/10/01 17:58:17]

Yupp, I edited the comment.

+  PAGE_LOAD_SUCCESSFUL_FIRST_LAYOUT_FG,
+  PAGE_LOAD_SUCCESSFUL_FIRST_LAYOUT_BG,

[Randy Smith (Not in Mondays), 2015/10/01 17:18:08]

We historically discourage abbreviations in chromium, so I'd recommend
FG->FOREGROUND, BG->BACKGROUND

+
+  // Add values before this final count. Make sure you also update
+  // histograms.xml.

[Randy Smith (Not in Mondays), 2015/10/01 17:18:09]

Actually, the note about the link to histograms.xml should be before the enum,
and it should also warn people not to *remove* values without revving the
histogram name.

[Charlie Harrison, 2015/10/01 17:58:17]

Done.

+  PAGE_LOAD_LAST_ENTRY
+};
+
 class PageLoadTracker {
  public:
   explicit PageLoadTracker(bool in_foreground);
@@ -33,6 +60,7 @@ class PageLoadTracker {
 
   // Returns true if the timing was successfully updated.
   bool UpdateTiming(const PageLoadTiming& timing);
+  void RecordEvent(PageLoadEvent event);
 
  private:
   void RecordTimingHistograms();