[ios] EarlGrey test for PDF Mime type.

ios/web/shell/test/earl_grey/shell_matchers.mm

Index: ios/web/shell/test/earl_grey/shell_matchers.mm
diff --git a/ios/web/shell/test/earl_grey/shell_matchers.mm b/ios/web/shell/test/earl_grey/shell_matchers.mm
index 055417cc4cfdd2b6e8c4d5e74c0fa1281aff7ebe..e88161c4d109bc198efc6c8813ccf2c4838c3f3f 100644
--- a/ios/web/shell/test/earl_grey/shell_matchers.mm
+++ b/ios/web/shell/test/earl_grey/shell_matchers.mm
@@ -27,6 +27,10 @@ id<GREYMatcher> webViewScrollView() {
   return [GREYMatchers matcherForWebViewScrollView];
 }
 
+id<GREYMatcher> webViewMimeType(const std::string& mime_type) {
+  return [GREYMatchers matcherForWebViewMIMETYPE:mime_type];
+}
+
 id<GREYMatcher> addressFieldText(const std::string& text) {
   return [GREYMatchers matcherForAddressFieldEqualToText:text];
 }
@@ -61,6 +65,11 @@ id<GREYMatcher> addressField() {
   return web::webViewScrollView(web::shell_test_util::GetCurrentWebState());
 }
 
++ (id<GREYMatcher>)matcherForWebViewMIMEType:(const std::string&)MIMEType {
+  web::WebState* webState = web::shell_test_util::GetCurrentWebState();
+  return web::webViewMimeType(MIMEType, webState);
+}
+
 + (id<GREYMatcher>)matcherForAddressFieldEqualToText:(const std::string&)text {
   MatchesBlock matches = ^BOOL(UIView* view) {
     if (![view isKindOfClass:[UITextField class]]) {