[MD Settings] Add title to show/hide password button.

chrome/app/settings_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Settings-specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- About Page -->
   <message name="IDS_SETTINGS_ABOUT_PAGE_BROWSER_VERSION" desc="The text label describing the version of the browser, example: Version 57.0.2937.0 (Developer Build) unknown (64-bit)">
     Version <ph name="PRODUCT_VERSION">$1<ex>15.0.865.0</ex></ph> (<ph name="PRODUCT_CHANNEL">$2<ex>Developer Build</ex></ph>) <ph name="PRODUCT_MODIFIER">$3</ph> <ph name="PRODUCT_VERSION_BITS">$4</ph>
   </message>
   <if expr="chromeos">
     <message name="IDS_SETTINGS_ABOUT_PAGE_DETAILED_BUILD_INFO" desc="Label describing the section that shows detailed information about the current Chrome build.">
       Detailed build information
@@ skipping 396 matching lines @@
   </message>
   <message name="IDS_SETTINGS_PASSWORD_DONE" desc="Label for a button that dismisses the password details dialog.">
     Done
   </message>
   <message name="IDS_SETTINGS_PASSWORD_REMOVE" desc="Label for a context menu item that removes the selected password." meaning="Remove selected password.">
     Remove
   </message>
   <message name="IDS_SETTINGS_PASSWORD_SEARCH" desc="Placeholder/label for the text input field that allows a user to filter saved passwords.">
     Search passwords
   </message>
+  <message name="IDS_SETTINGS_PASSWORD_SHOW" desc="Label for a tool tip on a button that reveals the saved password.">

[dschuyler, 2017/02/15 20:12:15]

"Label for" seems redundant with "a tool tip" consider
s/Label for a/A/

Same for the message below.

[hcarmona, 2017/02/15 21:52:10]

Done.

+    Show password
+  </message>
+  <message name="IDS_SETTINGS_PASSWORD_HIDE" desc="Label for a tool tip on a button that hides the saved password that is being shown.">
+    Hide password
+  </message>
   <message name="IDS_SETTINGS_PASSWORDS_VIEW_DETAILS_TITLE" desc="Title for the dialog that shows password details. This dialog lets a user see a saved password and copy the username.">
     Saved password details
   </message>
   <message name="IDS_SETTINGS_PASSWORD_VIEW_DETAILS" desc="Label for a context menu item that shows a dialog with details for the selected password.">
     View details
   </message>
   <message name="IDS_SETTINGS_PASSWORDS_WEBSITE" desc="Label for the website a password is for when editing a password.">
     Website
   </message>
   <message name="IDS_SETTINGS_PASSWORDS_USERNAME" desc="Label for the saved username when editing a password.">
@@ skipping 2426 matching lines @@
       System
     </message>
     <message name="IDS_SETTINGS_SYSTEM_HARDWARE_ACCELERATION_LABEL" desc="Label for the checkbox that forces Chrome to render via hardware acceleration (GPU) when available.">
       Use hardware acceleration when available
     </message>
     <message name="IDS_SETTINGS_SYSTEM_PROXY_SETTINGS_BUTTON" desc="Text for the button that changes a user's network proxy settings.">
       Change proxy settings
     </message>
   </if>
 </grit-part>