Remove the allow-displaying-mixed-content setting from Blink.

third_party/WebKit/LayoutTests/http/tests/security/mixedContent/insecure-image-in-main-frame-blocked.html

Index: third_party/WebKit/LayoutTests/http/tests/security/mixedContent/insecure-image-in-main-frame-blocked.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/insecure-image-in-main-frame-blocked.html b/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/insecure-image-in-main-frame-blocked.html
index 26c9576b0cf2c175b35e3490d92c8ca3a9db2281..b60f873fca6ca4139e7d0c986788f9cd10da28af 100644
--- a/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/insecure-image-in-main-frame-blocked.html
+++ b/third_party/WebKit/LayoutTests/http/tests/security/mixedContent/insecure-image-in-main-frame-blocked.html
@@ -6,7 +6,7 @@ if (window.testRunner) {
     testRunner.dumpAsText();
     testRunner.setCanOpenWindows();
     testRunner.setCloseRemainingWindowsWhenComplete(true);
-    testRunner.overridePreference("WebKitAllowDisplayingInsecureContent", false);
+    testRunner.overridePreference("WebKitStrictMixedContentChecking", true);
 }
 
 window.addEventListener("message", function (e) {
@@ -16,9 +16,8 @@ window.addEventListener("message", function (e) {
 
 </script>
 <p>This test opens a window that loads an insecure image.  We should not
-trigger a mixed content callback even though the main frame in the window
-is HTTPS and is displaying insecure content, because we've set the preference
-to block this.</p>
+trigger a mixed content callback because we've set the preference to block all
+mixed content, including passive content.</p>
 <script>
 window.open("https://127.0.0.1:8443/security/mixedContent/resources/frame-with-insecure-image.html");
 </script>