Add a refresh button for providers which do not support watchers.

ui/file_manager/file_manager/main.html

Index: ui/file_manager/file_manager/main.html
diff --git a/ui/file_manager/file_manager/main.html b/ui/file_manager/file_manager/main.html
index b101b69b39cb48c6c43f1e3cb9cfe89f6f7988ef..ea656da80168adacc2301129e0b56e42e6395150 100644
--- a/ui/file_manager/file_manager/main.html
+++ b/ui/file_manager/file_manager/main.html
@@ -54,6 +54,8 @@
       <command id="rename" i18n-values="label:RENAME_BUTTON_LABEL"
                shortcut="Enter-Ctrl">
       <command id="delete" shortcut="U+007F">
+      <command id="refresh" i18n-values="label:REFRESH_BUTTON_LABEL"
+               shortcut="U+0042-Ctrl">
       <command id="create-folder-shortcut"
                i18n-values="label:CREATE_FOLDER_SHORTCUT_BUTTON_LABEL">
       <command id="remove-folder-shortcut"
@@ -238,6 +240,11 @@
         <paper-ripple fit class="recenteringTouch"></paper-ripple>
         <div class="icon"></div>
       </button>
+      <button id="refresh-button" class="icon-button" tabindex="14"

[fukino, 2015/07/01 10:39:33]

I'm not sure where we should put the refresh button.

Buttons on the left side of search have been actions for selected files.
Right side to the search button might be better for "refresh"?

It's getting many buttons on the toolbar.
Putting "refresh" on the gear menu might be an another option.

Alternatively/Additionally, Ctrl+R for refresh might be convenient.

As there are some points to be discussed, I'd like a separated crbug issue to
discuss the UI for refreshing the directory with ben and seb.

[mtomasz, 2015/07/02 08:52:40]

I also agree there is many buttons now, but it will show only for providers
which do not support file watchers. Putting it to the gear menu will on the
other hand grow the menu + it may not be discoverable.

To make the buttons easier to understand I suggest adding tooltips -
crbug.com/506100.

We can confirm with Sebastien but from the crbug.com I assumed he's fine with
the button in the toolbar. Let's ask him for confirmation.

+              command="#refresh">
+        <paper-ripple fit class="recenteringTouch"></paper-ripple>
+        <div class="icon"></div>
+      </button>
       <button id="search-button" class="icon-button" tabindex="12"
               i18n-values="aria-label:SEARCH_TEXT_LABEL">
         <files-toggle-ripple></files-toggle-ripple>
@@ -256,7 +263,7 @@
         <div class="buttons">
           <button id="cloud-import-button"
                   class="icon-button manual-display"
-                  tabindex="14"
+                  tabindex="15"

[fukino, 2015/07/01 10:39:33]

Could you update go/filesapp-tabindex?
It seems tab index of directory tree and "check eligibility" button need to be
updated.

[mtomasz, 2015/07/02 08:52:40]

Done.

                   i18n-values="aria-label:CLOUD_IMPORT_COMMAND">
             <iron-icon icon="cloud-queue"></iron-icon>
           </button>
@@ -272,19 +279,19 @@
           <files-toggle-ripple></files-toggle-ripple>
         </div>
       </div>
-      <button id="view-button" class="icon-button" tabindex="15"
+      <button id="view-button" class="icon-button" tabindex="16"
               i18n-values="aria-label:CHANGE_TO_THUMBNAILVIEW_BUTTON_LABEL">
         <paper-ripple fit class="recenteringTouch"></paper-ripple>
         <div class="icon"></div>
       </button>
-      <button id="sort-button" class="icon-button" tabindex="16"
+      <button id="sort-button" class="icon-button" tabindex="17"
               menu="#sort-menu"
               i18n-values="aria-label:SORT_BUTTON_TOOLTIP"
               aria-activedescendant="sort-menu">
         <files-toggle-ripple></files-toggle-ripple>
         <div class="icon"></div>
       </button>
-      <button id="gear-button" class="icon-button" tabindex="17"
+      <button id="gear-button" class="icon-button" tabindex="18"
               menu="#gear-menu"
               i18n-values="aria-label:GEAR_BUTTON_TOOLTIP"
               aria-activedescendant="gear-menu">