PlzNavigate: Move navigation-level mixed content checks to the browser.

third_party/WebKit/Source/core/loader/MixedContentChecker.h

Index: third_party/WebKit/Source/core/loader/MixedContentChecker.h
diff --git a/third_party/WebKit/Source/core/loader/MixedContentChecker.h b/third_party/WebKit/Source/core/loader/MixedContentChecker.h
index b1100e79ab882ec943879713013455ee27fcc21d..6995cd20f6984236d5513d5e21b05d7ab62ffb3a 100644
--- a/third_party/WebKit/Source/core/loader/MixedContentChecker.h
+++ b/third_party/WebKit/Source/core/loader/MixedContentChecker.h
@@ -47,6 +47,12 @@ class KURL;
 class ResourceResponse;
 class SecurityOrigin;
 
+// Checks all sub-resource loads for mixed-content. Frame-level loads are
+// checked at the browser by MixedContentNavigationThrottle. Changes to this
+// class might need to be reflected on its browser counterpart.
+//
+// Current mixed content draft that drives this implementation:
+// https://w3c.github.io/webappsec-mixed-content/
 class CORE_EXPORT MixedContentChecker final {
   WTF_MAKE_NONCOPYABLE(MixedContentChecker);
   DISALLOW_NEW();