[ios] EarlGrey test for PDF Mime type.

ios/web/public/test/earl_grey/web_view_matchers.mm

Index: ios/web/public/test/earl_grey/web_view_matchers.mm
diff --git a/ios/web/public/test/earl_grey/web_view_matchers.mm b/ios/web/public/test/earl_grey/web_view_matchers.mm
index b75a1655b568d305f755e8fd7a0c24e6b3937024..01b2fafb14f21d0bb9f26248c12ac9fd472406d7 100644
--- a/ios/web/public/test/earl_grey/web_view_matchers.mm
+++ b/ios/web/public/test/earl_grey/web_view_matchers.mm
@@ -79,6 +79,11 @@ id<GREYMatcher> webViewScrollView(web::WebState* webState) {
   return [GREYMatchers matcherForWebViewScrollViewInWebState:webState];
 }
 
+id<GREYMatcher> webViewMimeType(const std::string& mimeType,
+                                web::WebState* webState) {
+  return [GREYMatchers matcherForWebViewMIMEType:mimeType inWebState:webState];
+}
+
 }  // namespace web
 
 @implementation GREYMatchers (WebViewAdditions)
@@ -163,4 +168,34 @@ id<GREYMatcher> webViewScrollView(web::WebState* webState) {
       autorelease];
 }
 
++ (id<GREYMatcher>)matcherForWebViewMIMEType:(const std::string&)MIMEType
+                                  inWebState:(web::WebState*)webState {
+  std::string MIMETypeCopy = MIMEType;
+  MatchesBlock matches = ^BOOL(UIView* view) {
+    __block BOOL didSucceed = NO;
+    NSDate* deadline =
+        [NSDate dateWithTimeIntervalSinceNow:testing::kWaitForUIElementTimeout];
+    while ([[NSDate date] compare:deadline] != NSOrderedDescending) {
+      if (webState->GetContentsMimeType() == MIMETypeCopy) {
+        didSucceed = YES;
+        break;
+      }
+      base::test::ios::SpinRunLoopWithMaxDelay(
+          base::TimeDelta::FromSecondsD(testing::kSpinDelaySeconds));
+    }
+    return didSucceed;
+  };
+
+  DescribeToBlock describe = ^(id<GREYDescription> description) {
+    [description appendText:@"web view MIME type "];
+    [description appendText:base::SysUTF8ToNSString(MIMETypeCopy)];
+  };
+
+  return grey_allOf(webViewInWebState(webState),
+                    [[[GREYElementMatcherBlock alloc]
+                        initWithMatchesBlock:matches
+                            descriptionBlock:describe] autorelease],
+                    nil);
+}
+
 @end