`about:blank` is not mixed content.

third_party/WebKit/Source/core/loader/MixedContentCheckerTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/loader/MixedContentChecker.h"
 
 #include "core/frame/Settings.h"
 #include "core/loader/EmptyClients.h"
 #include "core/testing/DummyPageHolder.h"
 #include "platform/network/ResourceResponse.h"
@@ skipping 10 matching lines @@
 TEST(MixedContentCheckerTest, IsMixedContent)
 {
     struct TestCase {
         const char* origin;
         const char* target;
         bool expectation;
     } cases[] = {
         {"http://example.com/foo", "http://example.com/foo", false},
         {"http://example.com/foo", "https://example.com/foo", false},
         {"http://example.com/foo", "data:text/html,<p>Hi!</p>", false},
+        {"http://example.com/foo", "about:blank", false},
         {"https://example.com/foo", "https://example.com/foo", false},
         {"https://example.com/foo", "wss://example.com/foo", false},
         {"https://example.com/foo", "data:text/html,<p>Hi!</p>", false},
         {"https://example.com/foo", "http://127.0.0.1/", false},
         {"https://example.com/foo", "http://[::1]/", false},
 
         {"https://example.com/foo", "http://example.com/foo", true},
         {"https://example.com/foo", "http://google.com/foo", true},
         {"https://example.com/foo", "ws://example.com/foo", true},
         {"https://example.com/foo", "ws://google.com/foo", true},
         {"https://example.com/foo", "http://192.168.1.1/", true},
         {"https://example.com/foo", "http://localhost/", true},
     };
 
-    for (size_t i = 0; i < WTF_ARRAY_LENGTH(cases); ++i) {
-        const char* origin = cases[i].origin;
-        const char* target = cases[i].target;
-        bool expectation = cases[i].expectation;
-
-        KURL originUrl(KURL(), origin);
+    for (const auto& test : cases) {
+        SCOPED_TRACE(::testing::Message() << "Origin: " << test.origin << ", Target: " << test.target << ", Expectation: " << test.expectation);
+        KURL originUrl(KURL(), test.origin);
         RefPtr<SecurityOrigin> securityOrigin(SecurityOrigin::create(originUrl));
-        KURL targetUrl(KURL(), target);
-        EXPECT_EQ(expectation, MixedContentChecker::isMixedContent(securityOrigin.get(), targetUrl)) << "Origin: " << origin << ", Target: " << target << ", Expectation: " << expectation;
+        KURL targetUrl(KURL(), test.target);
+        EXPECT_EQ(test.expectation, MixedContentChecker::isMixedContent(securityOrigin.get(), targetUrl));
     }
 }
 
 TEST(MixedContentCheckerTest, ContextTypeForInspector)
 {
     std::unique_ptr<DummyPageHolder> dummyPageHolder = DummyPageHolder::create(IntSize(1, 1));
     dummyPageHolder->frame().document()->setSecurityOrigin(SecurityOrigin::createFromString("http://example.test"));
 
     ResourceRequest notMixedContent("https://example.test/foo.jpg");
     notMixedContent.setFrameType(WebURLRequest::FrameTypeAuxiliary);
@@ skipping 47 matching lines @@
     ResourceResponse response2;
     WebURLRequest::RequestContext requestContext = WebURLRequest::RequestContextImage;
     ASSERT_EQ(WebMixedContent::ContextType::OptionallyBlockable, WebMixedContent::contextTypeFromRequestContext(requestContext, dummyPageHolder->frame().settings()->strictMixedContentCheckingForPlugin()));
     response2.setURL(displayedUrl);
     response2.setSecurityInfo("security info2");
     EXPECT_CALL(*client, didDisplayContentWithCertificateErrors(displayedUrl, response2.getSecurityInfo()));
     MixedContentChecker::handleCertificateError(&dummyPageHolder->frame(), response2, WebURLRequest::FrameTypeNone, requestContext);
 }
 
 } // namespace blink