Properly check the visibility of elements in browsertests

No change in production logic.

Visibility of elements must be checked by recursively checking the
visibility of parent elements, since any element inside an invisible
element will also be invisible.

This issue does not present itself in the Desktop layout, because
.hidden is defined differently (with display: none). Since the mobile
layout defines it with opacity, we need to recursively check parents.

It's not sufficient to check the opacity value itself, because CSS
transitions may not have finished by the time we check. Instead, we
simply check the CSS class and trust it to hide things properly.

BUG=716542

Review-Url: https://codereview.chromium.org/2845423002
Cr-Commit-Position: refs/heads/master@{#468111}

chrome/browser/safe_browsing/safe_browsing_blocking_page_test.cc

@@ -562,13 +562,26 @@ class SafeBrowsingBlockingPageBrowserTest
     if (!rfh)
       return VISIBILITY_ERROR;
 
-    std::unique_ptr<base::Value> value = content::ExecuteScriptAndGetValue(
-        rfh, "var node = document.getElementById('" + node_id +
-                 "');\n"
-                 "if (node)\n"
-                 "   node.offsetWidth > 0 && node.offsetHeight > 0;"
-                 "else\n"
-                 "  'node not found';\n");
+    // clang-format off
+    std::string jsFindVisibility = R"(
+      (function isNodeVisible(node) {
+        if (!node) return 'node not found';
+        if (node.offsetWidth === 0 || node.offsetHeight === 0) return false;
+        // Do not check opacity, since the css transition may actually leave
+        // opacity at 0 after it's been unhidden
+        if (node.classList.contains('hidden')) return false;
+        // Otherwise, we must check all parent nodes
+        var parentVisibility = isNodeVisible(node.parentElement);
+        if (parentVisibility === 'node not found') {
+          return true; // none of the parents are set invisible
+        }
+        return parentVisibility;
+      }(document.getElementById(')" + node_id + R"(')));)";
+    // clang-format on
+
+    std::unique_ptr<base::Value> value =
+        content::ExecuteScriptAndGetValue(rfh, jsFindVisibility);
+
     if (!value.get())
       return VISIBILITY_ERROR;