Use blocking worker pool for sync file operations in Pepper.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 6ef49c9c3de79d833482fb65f1a409846caedb08..62abbd73763443741f70437bc71d9c5d15312e90 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -2342,6 +2342,8 @@ void WebContentsImpl::OnSetSelectedColorInColorChooser(int color_chooser_id,
 void WebContentsImpl::OnPepperPluginHung(int plugin_child_id,
                                          const FilePath& path,
                                          bool is_hung) {
+  UMA_HISTOGRAM_COUNTS("Pepper.PluginHung", 1);
+
   FOR_EACH_OBSERVER(WebContentsObserver, observers_,
                     PluginHungStatusChanged(plugin_child_id, path, is_hung));
 }