Reland "Add HTTPDangerWarning experiment to field trial testing config"

This is a reland of 702cbe72

The original change was reverted due to failures of the changed tests on trunk
(see crbug.com/1029292), so this updated CL uses conditional expectations based
on whether the feature is enabled.

Original change's description:
> Add HTTPDangerWarning experiment to field trial testing config
>
> Bug: 1027626
> Change-Id: I70ddfb8cb18b7e045e8c6f30ce7d398d0c2f1c1b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1929862
> Reviewed-by: Brian White <bcwhite@chromium.org>
> Reviewed-by: Carlos IL <carlosil@chromium.org>
> Reviewed-by: Steven Holte <holte@chromium.org>
> Commit-Queue: Livvie Lin <livvielin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#719730}

Bug: 1027626
Change-Id: I16415497b537b1350af79c88f76a03ef48ae488c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1946671Reviewed-by: Carlos IL <carlosil@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Livvie Lin <livvielin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721006}

chrome/browser/ssl/security_state_tab_helper_browsertest.cc

@@ -180,6 +180,22 @@ security_state::SecurityLevel GetLevelForPassiveMixedContent() {
              : security_state::NONE;
 }
 
+blink::SecurityStyle GetSecurityStyleForHttp() {
+  bool http_danger_warning_enabled = false;
+  if (base::FeatureList::IsEnabled(
+          security_state::features::kMarkHttpAsFeature)) {
+    std::string parameter = base::GetFieldTrialParamValueByFeature(
+        security_state::features::kMarkHttpAsFeature,
+        security_state::features::kMarkHttpAsFeatureParameterName);
+    if (parameter ==
+        security_state::features::kMarkHttpAsParameterDangerWarning) {
+      http_danger_warning_enabled = true;
+    }
+  }
+  return http_danger_warning_enabled ? blink::SecurityStyle::kInsecure
+                                     : blink::SecurityStyle::kNeutral;
+}
+
 // A delegate class that allows emulating selection of a file for an
 // INPUT TYPE=FILE form field.
 class FileChooserDelegate : public content::WebContentsDelegate {
@@ -1108,7 +1124,9 @@ IN_PROC_BROWSER_TEST_F(SecurityStateTabHelperTest,
   // Ensure that WebContentsObservers don't show an incorrect Form Not Secure
   // explanation. Regression test for https://crbug.com/691412.
   EXPECT_EQ(0u, observer.latest_explanations().neutral_explanations.size());
-  EXPECT_EQ(blink::SecurityStyle::kNeutral, observer.latest_security_style());
+  // The below expectation is based on the feature flag set in the field trial
+  // testing config.
+  EXPECT_EQ(GetSecurityStyleForHttp(), observer.latest_security_style());
 
   content::NavigationEntry* entry = contents->GetController().GetVisibleEntry();
   ASSERT_TRUE(entry);
@@ -1230,7 +1248,9 @@ IN_PROC_BROWSER_TEST_F(SecurityStateTabHelperTest,
   // Ensure that WebContentsObservers don't show an incorrect Form Not Secure
   // explanation. Regression test for https://crbug.com/691412.
   EXPECT_EQ(0u, observer.latest_explanations().neutral_explanations.size());
-  EXPECT_EQ(blink::SecurityStyle::kNeutral, observer.latest_security_style());
+  // The below expectation is based on the feature flag set in the field trial
+  // testing config.
+  EXPECT_EQ(GetSecurityStyleForHttp(), observer.latest_security_style());
 
   content::NavigationEntry* entry = contents->GetController().GetVisibleEntry();
   ASSERT_TRUE(entry);
@@ -1640,7 +1660,9 @@ IN_PROC_BROWSER_TEST_F(
 
   GURL mixed_content_url(https_server_.GetURL(replacement_path));
   ui_test_utils::NavigateToURL(browser(), mixed_content_url);
-  EXPECT_EQ(blink::SecurityStyle::kNeutral, observer.latest_security_style());
+  // The below expectation is based on the feature flag set in the field trial
+  // testing config.
+  EXPECT_EQ(GetSecurityStyleForHttp(), observer.latest_security_style());
 
   const content::SecurityStyleExplanations& mixed_content_explanation =
       observer.latest_explanations();

testing/variations/fieldtrial_testing_config.json

@@ -2900,7 +2900,7 @@
             ]
         }
     ],
-    "HTTPReallyBadFinal": [
+    "HTTPDangerWarning": [
         {
             "platforms": [
                 "android",
@@ -2914,7 +2914,7 @@
                 {
                     "name": "enabled",
                     "params": {
-                        "treatment": "dangerous"
+                        "treatment": "danger-warning"
                     },
                     "enable_features": [
                         "MarkHttpAs"