Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

components/startup_metric_utils/browser/startup_metric_utils.h

Index: components/startup_metric_utils/browser/startup_metric_utils.h
diff --git a/components/startup_metric_utils/browser/startup_metric_utils.h b/components/startup_metric_utils/browser/startup_metric_utils.h
index 5ebb8ff5e77c397d7aeb649c001260765e611f68..2f235b3056128354cc0a853242dcfecd74847485 100644
--- a/components/startup_metric_utils/browser/startup_metric_utils.h
+++ b/components/startup_metric_utils/browser/startup_metric_utils.h
@@ -30,10 +30,9 @@ enum class WebContentsWorkload {
 // Registers startup related prefs in |registry|.
 void RegisterPrefs(PrefRegistrySimple* registry);
 
-// Returns true if any UI other than the browser window has been displayed
-// so far.  Useful to test if UI has been displayed before the first browser
-// window was shown, which would invalidate any surrounding timing metrics.
-bool WasNonBrowserUIDisplayed();
+// Returns true when browser UI was not launched normally: some other UI was
+// shown first or browser was launched in background mode.
+bool WasMainWindowStartupInterrupted();
 
 // Call this when displaying UI that might potentially delay startup events.
 //
@@ -43,6 +42,10 @@ bool WasNonBrowserUIDisplayed();
 // been displayed or not.
 void SetNonBrowserUIDisplayed();
 
+// Call this when background mode gets enabled, as it might delay startup
+// events.
+void SetBackgroundModeEnabled();
+
 // Call this with the creation time of the startup (initial/main) process.
 void RecordStartupProcessCreationTime(const base::Time& time);
 
@@ -92,6 +95,15 @@ void RecordFirstWebContentsMainNavigationStart(const base::TimeTicks& ticks,
 // its navigation for the main frame.
 void RecordFirstWebContentsMainNavigationFinished(const base::TimeTicks& ticks);
 
+// Call this with the time when the Browser window painted its children for the
+// first time.
+void RecordBrowserWindowFirstPaint(const base::TimeTicks& ticks);
+
+// Call this with the time when the Browser window painted its children for the
+// first time and we got a CompositingEnded after that.
+void RecordBrowserWindowFirstPaintCompositingEnded(
+    const base::TimeTicks& ticks);
+
 // Returns the TimeTicks corresponding to main entry as recorded by
 // RecordMainEntryPointTime. Returns a null TimeTicks if a value has not been
 // recorded yet. This method is expected to be called from the UI thread.