Harden charset-as-string taking function deprecations.

Fix usages in compiler.

libraries/stdlib/test/io/Files.kt

@@ -352,19 +352,19 @@ class FilesTest {
     @test fun testCopyTo() {
         val srcFile = createTempFile()
         val dstFile = createTempFile()
-        srcFile.writeText("Hello, World!", "UTF8")
+        srcFile.writeText("Hello, World!")
         assertFailsWith(FileAlreadyExistsException::class) {
             srcFile.copyTo(dstFile)
         }
 
         var len = srcFile.copyTo(dstFile, overwrite = true)
         assertEquals(13L, len)
-        assertEquals(srcFile.readText(), dstFile.readText("UTF8"))
+        assertEquals(srcFile.readText(), dstFile.readText(Charsets.UTF_8))
 
         assertTrue(dstFile.delete())
         len = srcFile.copyTo(dstFile)
         assertEquals(13L, len)
-        assertEquals(srcFile.readText("UTF8"), dstFile.readText())
+        assertEquals(srcFile.readText(Charsets.UTF_8), dstFile.readText())
 
         assertTrue(dstFile.delete())
         dstFile.mkdir()
@@ -395,7 +395,7 @@ class FilesTest {
         val srcFile = createTempFile()
         val dstFile = createTempFile(directory = currentDir)
         try {
-            srcFile.writeText("Hello, World!", "UTF8")
+            srcFile.writeText("Hello, World!", Charsets.UTF_8)
             dstFile.delete()
 
             val dstRelative = File(dstFile.name)

libraries/stdlib/test/io/ReadWrite.kt

@@ -15,12 +15,12 @@ fun sample(): Reader = StringReader("Hello\nWorld");
 class ReadWriteTest {
     @test fun testAppendText() {
         val file = File.createTempFile("temp", System.nanoTime().toString())
-        file.writeText("Hello\n", "UTF8")
-        file.appendText("World\n", "UTF8")
+        file.writeText("Hello\n")
+        file.appendText("World\n")
         file.appendText("Again")
 
         assertEquals("Hello\nWorld\nAgain", file.readText())
-        assertEquals(listOf("Hello", "World", "Again"), file.readLines("UTF8"))
+        assertEquals(listOf("Hello", "World", "Again"), file.readLines(Charsets.UTF_8))
         file.deleteOnExit()
     }
 
@@ -145,7 +145,7 @@ class ReadWriteTest {
         val url = URL("http://kotlinlang.org")
         val text = url.readText()
         assertFalse(text.isEmpty())
-        val text2 = url.readText("UTF8")
+        val text2 = url.readText(charset("UTF8"))
         assertFalse(text2.isEmpty())
     }
 }

libraries/stdlib/test/text/StringJVMTest.kt

@@ -74,10 +74,8 @@ class StringJVMTest {
     }
 
     @test fun toByteArrayEncodings() {
-        val s = "hello"
-        val defaultCharset = java.nio.charset.Charset.defaultCharset()!!
-        assertEquals(String(s.toByteArray()), String(s.toByteArray(defaultCharset)))
-        assertEquals(String(s.toByteArray()), String(s.toByteArray(defaultCharset.name())))
+        val s = "hello®"
+        assertEquals(String(s.toByteArray()), String(s.toByteArray(Charsets.UTF_8)))
     }
 
     @test fun toCharArray() {