Add the Windows.IsPinnedToTaskbar metric.

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc

Index: chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
diff --git a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
index 281945d5632b740b9d39d69e3894c66a87a1cf74..8fd26a61a391fd9844ab957b1ca6f885b88ea81a 100644
--- a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
+++ b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
@@ -52,6 +52,7 @@
 
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
+#include "chrome/browser/shell_integration_win.h"
 #include "chrome/installer/util/google_update_settings.h"
 #endif  // defined(OS_WIN)
 
@@ -150,6 +151,7 @@ void RecordStartupMetricsOnBlockingPool() {
                             base::win::VERSION_WIN_LAST);
   UMA_HISTOGRAM_BOOLEAN("Windows.InCompatibilityMode",
                         os_info.version() != os_info.Kernel32Version());
+  shell_integration::win::RecordIsPinnedToTaskbarHistogram();

[gab, 2016/06/28 20:59:18]

Feels overkill to bounce to the BlockingPool only to have this post a task to
the IO thread. I think PostBrowserStart() below should post a delayed task
directly on the IO thread.

[Patrick Monette, 2016/06/28 23:22:24]

Done.

 #endif  // defined(OS_WIN)
 
 #if defined(OS_MACOSX)