Fix missing background images in Sync confirmation WebUI.

Before r705637, these images were inlined with Grit's flattenhtml attribute.
After that CL, flattenhtml was removed, but the images were not registered
with the corresponding WebUIDataSource, resulting in a broken URL request
for chrome://sync-confirmation/images/sync_confirmation_illustration.svg

Fixing by individually registering those images with the WebUIDataSource.

Fixes: 1014447
Change-Id: I198b99030f46fccc7dc38ad6d80a7a89da2a9ac3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863350
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706140}

chrome/browser/browser_resources.grd

@@ -332,6 +332,8 @@
         <include name="IDR_SYNC_CONFIRMATION_JS" file="resources\signin\sync_confirmation\sync_confirmation.js" type="BINDATA" />
         <include name="IDR_SYNC_CONFIRMATION_BROWSER_PROXY_JS" file="resources\signin\sync_confirmation\sync_confirmation_browser_proxy.js" type="BINDATA" />
         <include name="IDR_SYNC_CONFIRMATION_APP_JS" file="${root_gen_dir}\chrome\browser\resources\signin\sync_confirmation\sync_confirmation_app.js" use_base_dir="false" preprocess="true" type="BINDATA" />
+        <include name="IDR_SYNC_CONFIRMATION_IMAGES_SYNC_CONFIRMATION_ILLUSTRATION_SVG" file="resources\signin\sync_confirmation\images\sync_confirmation_illustration.svg" type="BINDATA" compress="gzip" />
+        <include name="IDR_SYNC_CONFIRMATION_IMAGES_SYNC_CONFIRMATION_ILLUSTRATION_DARK_SVG" file="resources\signin\sync_confirmation\images\sync_confirmation_illustration_dark.svg" type="BINDATA" compress="gzip" />
         <include name="IDR_SIGNIN_EMAIL_CONFIRMATION_HTML" file="resources\signin\signin_email_confirmation\signin_email_confirmation.html" flattenhtml="true" allowexternalscript="true" type="BINDATA" />
         <include name="IDR_SIGNIN_EMAIL_CONFIRMATION_JS" file="resources\signin\signin_email_confirmation\signin_email_confirmation.js" type="BINDATA" />
         <include name="IDR_SIGNIN_ERROR_HTML" file="resources\signin\signin_error\signin_error.html" flattenhtml="true" allowexternalscript="true" type="BINDATA" />

chrome/browser/ui/webui/signin/sync_confirmation_ui.cc

@@ -51,6 +51,13 @@ SyncConfirmationUI::SyncConfirmationUI(content::WebUI* web_ui)
                             IDR_SYNC_CONFIRMATION_APP_JS);
     source->AddResourcePath("sync_confirmation.js", IDR_SYNC_CONFIRMATION_JS);
 
+    source->AddResourcePath(
+        "images/sync_confirmation_illustration.svg",
+        IDR_SYNC_CONFIRMATION_IMAGES_SYNC_CONFIRMATION_ILLUSTRATION_SVG);
+    source->AddResourcePath(
+        "images/sync_confirmation_illustration_dark.svg",
+        IDR_SYNC_CONFIRMATION_IMAGES_SYNC_CONFIRMATION_ILLUSTRATION_DARK_SVG);
+
     AddStringResource(source, "syncConfirmationTitle",
                       IDS_SYNC_CONFIRMATION_TITLE);
     AddStringResource(source, "syncConfirmationSyncInfoTitle",