Add a histogram for each time the HTTP Bad UI is shown

chrome/browser/ssl/chrome_security_state_model_client.cc

Index: chrome/browser/ssl/chrome_security_state_model_client.cc
diff --git a/chrome/browser/ssl/chrome_security_state_model_client.cc b/chrome/browser/ssl/chrome_security_state_model_client.cc
index 5b7097e4b4e89c8b0c8ad8d31ffc030aa4cd8fbe..1db3e3c052e96879422d14e2f0ed1bb29732025b 100644
--- a/chrome/browser/ssl/chrome_security_state_model_client.cc
+++ b/chrome/browser/ssl/chrome_security_state_model_client.cc
@@ -338,14 +338,17 @@ void ChromeSecurityStateModelClient::VisibleSSLStateChanged() {
     return;
 
   std::string warning;
+  bool warning_is_user_visible = false;
   switch (security_info.security_level) {
     case security_state::SecurityStateModel::HTTP_SHOW_WARNING:
       warning =
           "This page includes a password or credit card input in a non-secure "
           "context. A warning has been added to the URL bar. For more "
           "information, see https://goo.gl/zmWq3m.";
+      warning_is_user_visible = true;
       break;
     case security_state::SecurityStateModel::NONE:
+    case security_state::SecurityStateModel::DANGEROUS:

[estark, 2016/10/26 21:29:46]

Two notes about this (no changes needed):

1. One could argue that this change belongs in a separate CL because it changes
functionality other than the main thing you're doing in this CL (which is adding
the histogram). Since it's so simple, I think it's fine to leave it here, just
making a note of it.

2. One could also argue that there should be a browser test for a console
message on DANGEROUS, along the lines of
https://cs.chromium.org/chromium/src/chrome/browser/ssl/chrome_security_state....
However... those tests are so long and ugly that I can't bear the thought of
adding another one. So I filed a bug for this missing test
(https://crbug.com/659801), blocking on a change that will allow these tests to
be much simpler (https://crbug.com/658099)

       warning =
           "This page includes a password or credit card input in a non-secure "
           "context. A warning will be added to the URL bar in Chrome 56 (Jan "
@@ -358,6 +361,8 @@ void ChromeSecurityStateModelClient::VisibleSSLStateChanged() {
   logged_http_warning_on_current_navigation_ = true;
   web_contents_->GetMainFrame()->AddMessageToConsole(
       content::CONSOLE_MESSAGE_LEVEL_WARNING, warning);
+  UMA_HISTOGRAM_BOOLEAN("Security.HTTPBad.UserWarnedAboutSensitiveInput",
+                        warning_is_user_visible);
 }
 
 void ChromeSecurityStateModelClient::DidFinishNavigation(