Reland "UTF-8 detector for pages missing encoding info"

third_party/WebKit/Source/core/html/parser/TextResourceDecoderTest.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/html/parser/TextResourceDecoder.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace blink {
+
+TEST(TextResourceDecoderTest, KeepEncodingConsistent)
+{
+    bool useAutoEncodingDetector = true;
+    OwnPtr<TextResourceDecoder> decoder = TextResourceDecoder::create("text/plain", WTF::TextEncoding(), useAutoEncodingDetector);
+
+    // First |decode()| call initializes the internal text codec with UTF-8
+    // which was inferred by the auto encoding detector.
+    decoder->decode("\xc2\xa7", 2);
+    ASSERT_EQ(UTF8Encoding(), decoder->encoding());
+
+    // Subsequent |decode()| is called with non-UTF-8 text (EUC-KR),
+    // but the codec remains fixed.
+    decoder->decode("\xc4\x22\xc4\x5c", 2);
+    EXPECT_EQ(UTF8Encoding(), decoder->encoding());
+
+    // |TextResourceDecoder| is created not to use auto encoding detector,
+    // which activates the light-weight UTF-8 encoding detector.
+    decoder = TextResourceDecoder::create("text/plain");
+
+    decoder->decode("abcde", 5);
+    ASSERT_EQ(Latin1Encoding(), decoder->encoding());
+
+    // Verify that the encoding(Latin1) used for the first |decode()| remains
+    // fixed even if the subsequent call is given UTF-8 text.
+    decoder->decode("\xc2\xa7", 2);
+    EXPECT_EQ(Latin1Encoding(), decoder->encoding());
+}
+}