Cros FilesApp ui test fixes

Change 'background-color:white' to apply to outer webview/iframe element
rather than inner body so that test page picks this up.

Add missing string.

Bug: 813477
Change-Id: I69d4827e4ec5dd4cc40b1ad229c6c8afd6e2254d
Reviewed-on: https://chromium-review.googlesource.com/1174578Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583147}

ui/file_manager/file_manager/foreground/elements/files_quick_view.css

@@ -113,6 +113,10 @@ paper-button:focus:not(:active) {
   width: 100%;
 }
 
+.text-content {
+  background-color: white;
+}
+
 #toolbar {
   align-items: center;
   background-color: rgb(40, 42, 45);

ui/file_manager/file_manager/foreground/elements/files_quick_view.html

@@ -36,7 +36,7 @@
           <div id="innerContentPanel" type$="[[type]]">
             <!-- PDF, Text -->
             <template is="dom-if" if="[[browsable]]">
-              <webview on-loadstart='applyTextCss' class="content" src="[[contentUrl]]"></webview>
+              <webview on-loadstart='applyTextCss' class="content text-content" src="[[contentUrl]]"></webview>
             </template>
             <!-- document/HTML -->
             <template is="dom-if" if="[[isHtml_(type, subtype)]]">

ui/file_manager/file_manager/foreground/elements/files_safe_text_webview_content.css

@@ -15,7 +15,6 @@ pre {
 }
 
 body {
-  background-color: white;
   /* properly set font size */
   font-size: medium;
   /* prevent overflowing to enable scrolling */

ui/file_manager/file_manager/test/js/strings.js

@@ -58,6 +58,7 @@ loadTimeData.data = new Proxy(
           'devices/goodies.html?utm_source=filesapp&utm_medium=banner&' +
           'utm_campaign=gsg',
       IMAGE_FILE_TYPE: '$1 image',
+      INSTALL_LINUX_PACKAGE_INSTALL_BUTTON: 'Install',
       INSTALL_NEW_EXTENSION_LABEL: 'Install new service',
       LINUX_FILES_ROOT_LABEL: 'Linux files',
       MANY_ENTRIES_SELECTED: '$1 items selected',