MD Settings: Fix Change Picture Camera icons.

Previously, the icon fill color was gray. This change restores it to
white, as the specs indicate.

BUG=NONE
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2528263003
Cr-Commit-Position: refs/heads/master@{#434841}

chrome/browser/resources/settings/people_page/camera.html

@@ -49,7 +49,7 @@
       }
 
       #flipPhoto {
-        color: white;
+        --iron-icon-fill-color: white;
         float: right;
       }
 
@@ -58,9 +58,9 @@
       }
 
       #takePhoto {
+        --iron-icon-fill-color: white;
         background-color: var(--paper-green-500);
         border-radius: 50%;
-        color: white;
         display: block;
         margin: 0 auto 0 auto;
       }

chrome/browser/resources/settings/people_page/change_picture.html

@@ -83,9 +83,9 @@
       }
 
       #discardOldImage {
+        --iron-icon-fill-color: white;
         background-color: var(--paper-red-500);
         border-radius: 50%;
-        color: white;
         display: block;
         margin: 0 auto 0 auto;
       }