PDF Viewer Update: Add aria-label for thumbnails

Bug: 652400
Change-Id: I44b3f9561c3186f9c40d52201ad4ec30b3f9c6a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2439433
Reviewed-by: Lei Zhang <[email protected]>
Reviewed-by: dpapad <[email protected]>
Commit-Queue: Daniel Hosseinian <[email protected]>
Cr-Commit-Position: refs/heads/master@{#812452}
diff --git a/components/pdf_strings.grdp b/components/pdf_strings.grdp
index f182b73..091531d 100644
--- a/components/pdf_strings.grdp
+++ b/components/pdf_strings.grdp
@@ -92,6 +92,9 @@
       =1 {PDF document containing {COUNT} page}
       other {PDF document containing {COUNT} pages}}
     </message>
+    <message name="IDS_PDF_THUMBNAIL_PAGE_ARIA_LABEL" desc="aria-label describing a thumbnail by its corresponding PDF page number">
+      Thumbnail for page <ph name="THUMBNAIL_PAGE"><ex>1</ex>$1</ph>
+    </message>
     <if expr="chromeos">
       <message name="IDS_PDF_DISCARD_FORM_CHANGES" desc="Title for a dialog that informs the user that the changes they have made to a form will be lost if they continue">
         Discard changes?