tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index bdb1c4f4214fe59cb48f4607fcc685c777ad8eac..418b21e3e04a4a66e63a25f96fac3188a2ac250f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3913,12 +3913,64 @@ other types of suffix sets.
   </summary>
 </histogram>
 
-<histogram name="FileBrowser.Load" units="milliseconds">
+<histogram name="FileBrowser.Load.AdditionalUI" units="milliseconds">
   <summary>
-    Chrome OS File Browser is an built-in extension without a background page.
-    Its main.html file is loaded every time the user opens a File Browser tab or
-    a file chooser dialog. The file is fairly large and the initialization is
-    pretty expensive.
+    Time to load additional UI elements during initialization of Files app. This
+    step loads all other UI elements, which do not require access to the file
+    system.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.Display" units="milliseconds">
+  <summary>
+    Time to display the most basic UI of Files.app (without the file list
+    loaded). This includes Load.General, Load.Strings and part of
+    Load.EssentialUI.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.EssentialUI" units="milliseconds">
+  <summary>
+    Time to load essential UI elements during initialization of Files app. This
+    step loads only these UI elements required to display the most basic UI.
+    File system may not be available yet, nor any other heavy elements.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.FileSystem" units="milliseconds">
+  <summary>
+    Time to load the file system during initialization of Files app.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.FileSystemUI" units="milliseconds">
+  <summary>
+    Time to load file system related UI elements during initialization of Files
+    app.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.General" units="milliseconds">
+  <summary>
+    Time to load essential data used by other steps of the initialization of
+    Files app. This is the first initialization step of Files app.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.Preference" units="milliseconds">
+  <summary>
+    Time to load preferences during initialization of Files app.
+  </summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.Strings" units="milliseconds">
+  <summary>Time to load strings during initialization of Files app.</summary>
+</histogram>
+
+<histogram name="FileBrowser.Load.Total" units="milliseconds">
+  <summary>
+    Total initialization initialization time of Files app. Includes all
+    initialization steps.
   </summary>
 </histogram>
 
@@ -4013,6 +4065,13 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="FileBrowser.RootsUpdateTime" units="milliseconds">
+  <summary>
+    Time to enumerate file system roots on initialziation or when a volume is
+    mounted or unmounted.
+  </summary>
+</histogram>
+
 <histogram name="FileBrowser.ViewingFileType" enum="ViewFileType">
   <summary>
     File types that were tried to be viewed through browser. This is recorded
@@ -23117,20 +23176,6 @@ other types of suffix sets.
   <affected-histogram name="Extensions.ExternalExtensionEvent"/>
 </fieldtrial>
 
-<fieldtrial name="FileBrowserLoad" separator=".">
-  <group name="Construct"
-      label="Time spent constructing the main Javascript object."/>
-  <group name="DOM" label="Time to initialize DOM."/>
-  <group name="FileSystem"
-      label="Time to get access to the local file system."/>
-  <group name="Parse" label="Time to parse Javascript and CSS."/>
-  <group name="Roots" label="Time to enumerate file system roots."/>
-  <group name="Total"
-      label="Total load time from the moment the Javascript started parsing
-             till the moment the empty file list is displayed."/>
-  <affected-histogram name="FileBrowser.Load"/>
-</fieldtrial>
-
 <fieldtrial name="HttpPipeliningCompatibility">
   <group name="disable_test" label="Do nothing"/>
   <group name="enable_test" label="Test connection for HTTP pipelining"/>