Extract colors from wallpaper and dynamically update login screen overlay

ui/login/account_picker/md_screen_account_picker.js

Index: ui/login/account_picker/md_screen_account_picker.js
diff --git a/ui/login/account_picker/md_screen_account_picker.js b/ui/login/account_picker/md_screen_account_picker.js
index 88ca6736d29011c8e2b851dff02530fac037c0be..e826ffbbb4c23545d2d152dbcb0e2ff9a432fd31 100644
--- a/ui/login/account_picker/md_screen_account_picker.js
+++ b/ui/login/account_picker/md_screen_account_picker.js
@@ -44,6 +44,7 @@ login.createScreen('AccountPickerScreen', 'account-picker', function() {
       'setPublicSessionLocales',
       'setPublicSessionKeyboardLayouts',
       'setLockScreenAppsState',
+      'setOverlayColors',
     ],
 
     preferredWidth_: 0,
@@ -81,6 +82,17 @@ login.createScreen('AccountPickerScreen', 'account-picker', function() {
       this.preferredHeight_ = height;
     },
 
+    /**
+     * Sets login screen overlay colors based on colors extracted from the
+     * wallpaper.
+     * @param {string} dmColor Color for the gradient mask.
+     * @param {string} scrollColor Color for the small pods container.
+     * @param {string} backgroundColor Color for the whole background.
+     */
+    setOverlayColors: function(dmColor, scrollColor, backgroundColor) {

[jdufault, 2017/06/12 21:37:29]

expand dm acronym 

[Wenzhao (Colin) Zang, 2017/06/12 23:40:35]

I changed it to maskColor which may make more sense for the user pod row.

+      $('pod-row').setOverlayColors(dmColor, scrollColor, backgroundColor);
+    },
+
     /**
      * When the account picker is being used to lock the screen, pressing the
      * exit accelerator key will sign out the active user as it would when