Test fixes

src/libraries/System.Console/tests/ReadAndWrite.cs

@@ -158,7 +158,9 @@ public static async Task OutWriteAndWriteLineOverloads()
                 Console.SetOut(sw);
                 TextWriter writer = Console.Out;
                 Assert.NotNull(writer);
-                Assert.NotEqual(writer, sw); // the writer we provide gets wrapped
+                // Browser bypasses SyncTextWriter for faster startup
+                if (!OperatingSystem.IsBrowser())
+                    Assert.NotEqual(writer, sw); // the writer we provide gets wrapped
 
                 // We just want to ensure none of these throw exceptions, we don't actually validate
                 // what was written.

src/libraries/System.Runtime/tests/System.IO.Tests/StreamReader/StreamReader.cs

@@ -30,6 +30,7 @@ public void ObjectClosedReadLineBaseStream()
         }
 
         [Fact]
+        [SkipOnPlatform(TestPlatforms.Browser, "Browser bypasses SyncTextWriter for faster startup")]
         public void Synchronized_NewObject()
         {
             using (Stream str = GetLargeStream())

src/libraries/System.Runtime/tests/System.IO.Tests/StreamWriter/StreamWriter.cs

@@ -8,6 +8,7 @@ namespace System.IO.Tests
     public partial class WriteTests
     {
         [Fact]
+        [SkipOnPlatform(TestPlatforms.Browser, "Browser bypasses SyncTextWriter for faster startup")]
         public void Synchronized_NewObject()
         {
             using (Stream str = CreateStream())

src/libraries/System.Runtime/tests/System.IO.Tests/TextWriter/TextWriterTests.cs

@@ -691,6 +691,7 @@ public void DisposeAsync_ExceptionReturnedInTask()
         }
 
         [Fact]
+        [SkipOnPlatform(TestPlatforms.Browser, "Browser bypasses SyncTextWriter for faster startup")]
         public async Task FlushAsync_Precanceled()
         {
             Assert.Equal(TaskStatus.RanToCompletion, TextWriter.Null.FlushAsync(new CancellationToken(true)).Status);