Update the Chromium-branded IDS_PRINT_PREVIEW_NO_PLUGIN message.

It now matches the Chrome-branded message. The messages used to be
different because the PDF plugin was proprietary, but we open sourced
the PDF plugin in 2014.

Change-Id: I1104911e60a1dcf61ef6194c91eecf67730e8c17
Reviewed-on: https://chromium-review.googlesource.com/1168650Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582712}

chrome/app/chromium_strings.grd

@@ -412,7 +412,7 @@ Chromium is unable to recover your settings.
 
       <!-- Print Preview -->
       <message name="IDS_PRINT_PREVIEW_NO_PLUGIN" desc="Message to display when the PDF viewer is missing.">
-        Chromium does not include the PDF viewer which is required for Print Preview to function.
+        Chromium cannot show the print preview when the built-in PDF viewer is missing.
       </message>
 
       <!-- Download Shelf Items -->

chrome/test/data/webui/print_preview/invalid_settings_browsertest.js

@@ -117,8 +117,8 @@ cr.define('invalid_settings_browsertest', function() {
         assertFalse(overlayEl.classList.contains('invisible'));
 
         // Make sure the correct text is shown.
-        const expectedMessageChromium = 'Chromium does not include the PDF ' +
-            'viewer which is required for Print Preview to function.';
+        const expectedMessageChromium = 'Chromium cannot show the print ' +
+            'preview when the built-in PDF viewer is missing.';
         const expectedMessageChrome = 'Google Chrome cannot show the print ' +
             'preview when the built-in PDF viewer is missing.';
         assertTrue(