Implementing mixed content for forms posting to insecure location from secure ones

Source/core/frame/UseCounter.h

Index: Source/core/frame/UseCounter.h
diff --git a/Source/core/frame/UseCounter.h b/Source/core/frame/UseCounter.h
index c887cb699e429adae53ce6d5d22e431a390dde57..cb2ad8c00b1c296aa371e5a190f4aaa0ed3a886a 100644
--- a/Source/core/frame/UseCounter.h
+++ b/Source/core/frame/UseCounter.h
@@ -434,6 +434,7 @@ public:
         FocusInOutEvent = 433,
         MouseEventMovementX = 434,
         MouseEventMovementY = 435,
+        MixedContentForm = 436,

[Mike West, 2014/06/06 12:18:18]

I should have been more clear: I think it would be valuable to split this
counter into three counters:

1. How many forms do we see, total?
2. How many mixed-content forms do we see?
3. How many mixed-content forms are submitted?

I'm not at all convinced that we'll be able to do anything with form submissions
without effecting some large subset of the web. I'm more optimistic about being
able to treat forms with insecure actions as passive mixed content. In order to
evaluate those, we'll need counters for both, and a baseline that tells us what
subset of the web we're effecting.

[mhm, 2014/06/06 19:11:59]

There is a counter already doing that (UseCounter::FormElement)
Now (UseCounter::MixedContentForm) is counting that.
Added (UseCounter::MixedContentSubmittedForm) for that.

         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         // Also, run update_use_counter_feature_enum.py in chromium/src/tools/metrics/histograms/