arc: Use static Play Store logo in OOBE.

This replaces external reference of Play Store logo in ARC OOBE OptIn to
internal static icon.

Test: Manually
Bug: 824952
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I351967a7b8738dbc1a7bd64adf0cf8c4d6b68926
Reviewed-on: https://chromium-review.googlesource.com/991470
Commit-Queue: Yury Khmel <khmel@google.com>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547825}

chrome/browser/resources/chromeos/login/screen_arc_terms_of_service.css

@@ -90,6 +90,10 @@
   margin: 0;
 }
 
+#arc-tos-legacy .oobe-icon {
+  -webkit-margin-start: -36px;
+}
+
 #arc-tos-loading,
 #arc-tos-error {
   -webkit-align-items: center;

chrome/browser/resources/chromeos/login/screen_arc_terms_of_service.html

 <link rel="stylesheet" href="chrome://resources/css/overlay.css">
+<link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 
 <div class="step right hidden arc-tos-loading no-logo" id="arc-tos"
     role="group" hidden>
   <arc-tos-md id="arc-tos-md" hidden></arc-tos-md>
   <div id="arc-tos-legacy">
     <div class="step-contents">
-      <img id="arc-tos-logo"
-          src="https://play.google.com/about/images/play_logo.png" alt>
+      <iron-icon src="chrome://oobe/playstore.svg" class="oobe-icon">
+      </iron-icon>
       <h1 i18n-content="arcTermsOfServiceScreenHeading"></h1>
       <h2 i18n-content="arcTermsOfServiceScreenDescription"></h2>
       <div id="arc-tos-container">

chrome/browser/resources/chromeos/login/screen_arc_terms_of_service.js

@@ -504,11 +504,6 @@ login.createScreen('ArcTermsOfServiceScreen', 'arc-tos', function() {
 
       Oobe.getInstance().headerHidden = true;
 
-      // Reload caption image in case it was not loaded during the
-      // initialization phase.
-      $('arc-tos-logo').src =
-          'https://play.google.com/about/images/play_logo.png';
-
       this.hideOverlay();
       // ToS content may be loaded before the page is shown. In that case,
       // height of ToS webview is not correctly caculated. Recaculate the