[chromium] Remove XMLViewer.js/css post blink-in-js migration of XML tree viewer.

CL, https://codereview.chromium.org/479753003, migrated the usage of XML tree viewer to
be implemented in blink-in-js. Post the migration, the files XMLViewer.js/css are no longer
used by any native code directly and hence should be removed.

Subsequent blink side CL would remove these files from the repository permanently.

TBR=jochen@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/540493002

Cr-Commit-Position: refs/heads/master@{#293303}

content/child/blink_platform_impl.cc

@@ -808,8 +808,6 @@ const DataResource kDataResources[] = {
   { "xhtmlmp.css", IDR_UASTYLE_XHTMLMP_CSS, ui::SCALE_FACTOR_NONE},
   { "viewportAndroid.css", IDR_UASTYLE_VIEWPORT_ANDROID_CSS,
     ui::SCALE_FACTOR_NONE},
-  { "XMLViewer.js", IDR_XML_VIEWER_JS, ui::SCALE_FACTOR_NONE },
-  { "XMLViewer.css", IDR_XML_VIEWER_CSS, ui::SCALE_FACTOR_NONE },
   { "InspectorOverlayPage.html", IDR_INSPECTOR_OVERLAY_PAGE_HTML,
     ui::SCALE_FACTOR_NONE },
   { "InjectedScriptCanvasModuleSource.js",