Implement StringImpl sharing for StringView::toString().

third_party/WebKit/Source/wtf/text/StringViewTest.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 "wtf/text/StringView.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/StringImpl.h"
 #include "wtf/text/WTFString.h"
@@ skipping 300 matching lines @@
     EXPECT_TRUE(StringView(String(kChars), 5).isEmpty());
     EXPECT_TRUE(StringView(String(kChars), 4, 0).isEmpty());
     EXPECT_TRUE(StringView().isEmpty());
     EXPECT_TRUE(StringView("").isEmpty());
     EXPECT_TRUE(StringView(reinterpret_cast<const UChar*>(u"")).isEmpty());
     EXPECT_FALSE(StringView(kChars16).isEmpty());
 }
 
 TEST(StringViewTest, ToString)
 {
-    // Empty string optimization.
     EXPECT_EQ(emptyString().impl(), StringView("").toString().impl());
+    EXPECT_EQ(nullAtom.impl(), StringView().toString().impl());
     // NOTE: All the construction tests also check toString().
 }
 
 TEST(StringViewTest, ToAtomicString)
 {
-    EXPECT_EQ(AtomicString(), nullAtom);
-    EXPECT_EQ(AtomicString(""), emptyAtom);
+    EXPECT_EQ(nullAtom.impl(), StringView().toAtomicString());
+    EXPECT_EQ(emptyAtom.impl(), StringView("").toAtomicString());
     EXPECT_EQ(AtomicString("12"), StringView(kChars8, 2).toAtomicString());
     // AtomicString will convert to 8bit if possible when creating the string.
-    EXPECT_EQ(AtomicString("12"), StringView(kChars16, 2).toAtomicString());
+    EXPECT_EQ(AtomicString("12").impl(), StringView(kChars16, 2).toAtomicString().impl());
+}
+
+TEST(StringViewTest, ToStringImplSharing)
+{
+    String string(kChars);
+    EXPECT_EQ(string.impl(), StringView(string).sharedImpl());
+    EXPECT_EQ(string.impl(), StringView(string).toString().impl());
+    EXPECT_EQ(string.impl(), StringView(string).toAtomicString().impl());
 }
 
 TEST(StringViewTest, NullString)
 {
     EXPECT_TRUE(StringView().isNull());
     EXPECT_TRUE(StringView(String()).isNull());
     EXPECT_TRUE(StringView(AtomicString()).isNull());
     EXPECT_TRUE(StringView(static_cast<const char*>(nullptr)).isNull());
     StringView view(kChars);
     EXPECT_FALSE(view.isNull());
@@ skipping 50 matching lines @@
 
     EXPECT_TRUE(equalIgnoringASCIICase(StringView("link"), "lInK"));
     EXPECT_FALSE(equalIgnoringASCIICase(StringView("link"), "INKL"));
     EXPECT_FALSE(equalIgnoringASCIICase(StringView("link"), "link different length"));
     EXPECT_FALSE(equalIgnoringASCIICase(StringView("link different length"), "link"));
 
     EXPECT_TRUE(equalIgnoringASCIICase(StringView(""), ""));
 }
 
 } // namespace WTF