Make WaitAssert report browser errors

It turns out we frequently have errors in the browser console in cases
where we're hitting a "timeout".

src/Shared/E2ETesting/BrowserAssertFailedException.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using Xunit.Sdk;
+
+namespace OpenQA.Selenium
+{
+    // Used to report errors when we find errors in the browser. This is useful
+    // because the underlying assert probably doesn't provide good information in that
+    // case.
+    public class BrowserAssertFailedException : XunitException
+    {
+        public BrowserAssertFailedException(IReadOnlyList<LogEntry> logs, Exception innerException)
+            : base(BuildMessage(logs), innerException)
+        {
+        }
+
+        private static string BuildMessage(IReadOnlyList<LogEntry> logs)
+        {
+            return
+                "Encountered browser errors while running assertion." + Environment.NewLine +
+                string.Join(Environment.NewLine, logs);
+        }
+    }
+}

src/Shared/E2ETesting/BrowserTestBase.cs

@@ -80,15 +80,14 @@ namespace Microsoft.AspNetCore.E2ETesting
 
         protected IWebElement WaitUntilExists(By findBy, int timeoutSeconds = 10, bool throwOnError = false)
         {
-            List<LogEntry> errors = null;
+            IReadOnlyList<LogEntry> errors = null;
             IWebElement result = null;
             new WebDriverWait(Browser, TimeSpan.FromSeconds(timeoutSeconds)).Until(driver =>
             {
                 if (throwOnError && Browser.Manage().Logs.AvailableLogTypes.Contains(LogType.Browser))
                 {
                     // Fail-fast if any errors were logged to the console.
-                    var log = Browser.Manage().Logs.GetLog(LogType.Browser);
-                    errors = log.Where(IsError).ToList();
+                    errors = Browser.GetBrowserLogs(LogLevel.Severe);
                     if (errors.Count > 0)
                     {
                         return true;

src/Shared/E2ETesting/WaitAssert.cs

@@ -73,7 +73,12 @@ namespace Microsoft.AspNetCore.E2ETesting
             }
             catch (WebDriverTimeoutException)
             {
-                if (lastException != null)
+                var errors = driver.GetBrowserLogs(LogLevel.Severe);
+                if (errors.Count > 0)
+                {
+                    throw new BrowserAssertFailedException(errors, lastException);
+                }
+                else if (lastException != null)
                 {
                     ExceptionDispatchInfo.Capture(lastException).Throw();
                 }

src/Shared/E2ETesting/WebDriverExtensions.cs

@@ -0,0 +1,58 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace OpenQA.Selenium
+{
+    public static class WebDriverExtensions
+    {
+        public static IReadOnlyList<LogEntry> GetBrowserLogs(this IWebDriver driver, LogLevel level)
+        {
+            if (driver is null)
+            {
+                throw new ArgumentNullException(nameof(driver));
+            }
+
+            // Fail-fast if any errors were logged to the console.
+            var log = driver.Manage().Logs.GetLog(LogType.Browser);
+            if (log == null)
+            {
+                return Array.Empty<LogEntry>();
+            }
+
+            var logs = log.Where(entry => entry.Level >= level && !ShouldIgnore(entry)).ToList();
+            if (logs.Count > 0)
+            {
+                return logs;
+            }
+
+            return Array.Empty<LogEntry>();
+        }
+
+        // Be careful adding anything new to this list. We only want to put things here that are ignorable
+        // in all cases.
+        private static bool ShouldIgnore(LogEntry entry)
+        {
+            // Don't fail if we're missing the favicon, that's not super important.
+            if (entry.Message.Contains("favicon.ico"))
+            {
+                return true;
+            }
+
+            // These two messages appear sometimes, but it doesn't actually block the tests.
+            if (entry.Message.Contains("WASM: wasm streaming compile failed: TypeError: Could not download wasm module"))
+            {
+                return true;
+            }
+            if (entry.Message.Contains("WASM: falling back to ArrayBuffer instantiation"))
+            {
+                return true;
+            }
+
+            return false;
+        }
+    }
+}