Add percentage of progress in notification header.

ui/strings/ui_strings.grd

Index: ui/strings/ui_strings.grd
diff --git a/ui/strings/ui_strings.grd b/ui/strings/ui_strings.grd
index 78f9fe70419cec30ec2bda192e785d1bc2076300..030189b9a3e121e0214bdd691a741fa6803989e8 100644
--- a/ui/strings/ui_strings.grd
+++ b/ui/strings/ui_strings.grd
@@ -631,6 +631,9 @@ need to be translated for each locale.-->
       <message name="IDS_MESSAGE_CENTER_CLEAR_ALL" desc="The button for clearing all notifications.">
         Clear All
       </message>
+      <message name="IDS_MESSAGE_CENTER_NOTIFICATION_HEADER_DIVIDER_SYMBOL_WITH_SPACES" desc="The divider symbol between different parts of the notification header including spaces." translateable="false">

[fukino, 2017/06/22 08:57:43]

translatable?

[tetsui, 2017/06/23 02:33:04]

Removed. FYI: even though translateable seems misspelling, it's correct in
grit... https://cs.chromium.org/search/?q=translateable+grd&type=cs

+        ''' • '''

[fukino, 2017/06/22 08:57:43]

I'm not sure if we can expect that all fonts we use have a glyph for •.
Maybe we should use an image for this separator?

[yoshiki, 2017/06/22 13:27:37]

Android uses character, so IMO this character is ok.
https://android.googlesource.com/platform/frameworks/base/+/master/core/res/r...

I think it's better to have it as a constant in source code. like:

base::char16 kNotificationHeaderDividerSymbol = 0x2022;

[tetsui, 2017/06/23 02:33:04]

Done.

+      </message>
       <if expr="not use_titlecase">
         <message name="IDS_MESSAGE_CENTER_QUIET_MODE_BUTTON_TOOLTIP" desc="The tooltip text for the do not disturb button.">
           Do not disturb