Fix broken mixed script Rappor metric and add browser test

chrome/renderer/content_settings_observer.cc

 // Copyright (c) 2012 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 "chrome/renderer/content_settings_observer.h"
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "components/content_settings/content/common/content_settings_messages.h"
 #include "content/public/common/url_constants.h"
@@ skipping 465 matching lines @@
                      base::CompareCase::INSENSITIVE_ASCII))
     SendInsecureContentSignal(INSECURE_CONTENT_RUN_JS);
   else if (base::EndsWith(resource_gurl.path(), kDotCSS,
                           base::CompareCase::INSENSITIVE_ASCII))
     SendInsecureContentSignal(INSECURE_CONTENT_RUN_CSS);
   else if (base::EndsWith(resource_gurl.path(), kDotSWF,
                           base::CompareCase::INSENSITIVE_ASCII))
     SendInsecureContentSignal(INSECURE_CONTENT_RUN_SWF);
 
   if (!allow_running_insecure_content_ && !allowed_per_settings) {
-    DidBlockContentType(CONTENT_SETTINGS_TYPE_MIXEDSCRIPT, origin.host());
+    DidBlockContentType(CONTENT_SETTINGS_TYPE_MIXEDSCRIPT, origin.toString());

[felt, 2016/06/10 03:41:08]

Man, this is a tricky bug. It wasn't obvious to me at first what was going on
with this bug (or bugfix). I think it's so tricky for two reasons:

1. It isn't particularly clear that this string is going to end up turned back
into a GURL.
2. I would have expected TabSpecificContentSettings::OnContentBlockedWithDetail
to DCHECK that GURL(base::UTF16ToUTF8(details)).is_valid(). This would ensure
that the contract was upheld by the caller a few layers back.

I'm not suggesting that we change anything, since the bug is now found and
fixed. However: it's something I'll keep in mind the next time I see a similar
pattern!

[estark, 2016/06/10 03:55:20]

Easy enough to add a DCHECK, so I did that. Also will crib jialiul's description
of the issue that she had put in the CL she started and put it in this one, so
that the fix is a bit easier to understand.

     return false;
   }
 
   return true;
 }
 
 bool ContentSettingsObserver::allowAutoplay(bool default_value) {
   if (!content_setting_rules_)
     return default_value;
 
@@ skipping 130 matching lines @@
 
   // If the scheme is file:, an empty file name indicates a directory listing,
   // which requires JavaScript to function properly.
   if (base::EqualsASCII(protocol, url::kFileScheme)) {
     return document_url.SchemeIs(url::kFileScheme) &&
            document_url.ExtractFileName().empty();
   }
 
   return false;
 }