Extract colors from wallpaper and dynamically update login screen overlay

ui/login/account_picker/md_user_pod_row.css

Index: ui/login/account_picker/md_user_pod_row.css
diff --git a/ui/login/account_picker/md_user_pod_row.css b/ui/login/account_picker/md_user_pod_row.css
index 9ffe3aa72479b02844621591344c1cc09a48427d..50a7e4b632cf41fb72a117c8af4d0737b3ad8df8 100644
--- a/ui/login/account_picker/md_user_pod_row.css
+++ b/ui/login/account_picker/md_user_pod_row.css
@@ -90,7 +90,7 @@ html[dir=rtl] .user-image-pane {
 
 .user-image {
   border-radius: 50%;
-  box-shadow: 0 0 2px rgba(255, 255, 255, .34);
+  box-shadow: 0 0 4px rgba(255, 255, 255, .34);
   height: 100%;
   width: 100%;
 }
@@ -210,8 +210,7 @@ html[dir=rtl] .main-pane {
   color: #FFFFFF;
   /* This should be 15.6px - the equivalent of 14px at 90% scale. */
   flex: auto;
-  font-family: "Roboto";
-  font-size: 24px;
+  font: 24px Roboto, sans-serif;
   outline: none;
   overflow: hidden;
   text-align: center;
@@ -1109,8 +1108,7 @@ html[dir=rtl] .expanded-pane {
 .small-pod-name {
   color: #FFFFFF;
   flex: auto;
-  font-family: "Roboto";
-  font-size: 20px;
+  font: 20px Roboto, sans-serif;
   height: 28px;
   left: 90px;
   opacity: 1;