Add a histogram to measure browser window display

chrome/browser/ui/browser.cc

Index: chrome/browser/ui/browser.cc
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 478acf76fe8a8eea71e4551f5d135f1655591199..6271aa3e16f5cf0845066591ed7d53d9da32a396 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -19,6 +19,7 @@
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/path_service.h"
+#include "base/process_info.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
@@ -1978,6 +1979,25 @@ void Browser::OnWindowDidShow() {
     return;
   window_has_shown_ = true;
 
+// CurrentProcessInfo::CreationTime() is currently only implemented on Mac and
+// Windows.
+#if defined(OS_MACOSX) || defined(OS_WIN)

[sky, 2012/06/26 16:14:15]

Aren't there a number of code paths that could result in showing non-browser
things for any length of time that end up skewing this number to be meaningless?

+  // Measure the latency from startup till the first browser window becomes
+  // visible.
+  static bool isFirstBrowserWindow = true;
+  if (isFirstBrowserWindow) {
+    isFirstBrowserWindow = false;
+    const base::Time* process_creation_time =
+        base::CurrentProcessInfo::CreationTime();
+
+    if (process_creation_time) {
+      UMA_HISTOGRAM_LONG_TIMES(
+          "Startup.BrowserWindowDisplay",
+          base::Time::Now() - *process_creation_time);
+    }
+  }
+#endif // OS_MACOSX || OS_WIN
+
   // Nothing to do for non-tabbed windows.
   if (!is_type_tabbed())
     return;