Use a Vector for the buffer in StringBuilder.

third_party/WebKit/Source/wtf/text/StringBuilderTest.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 99 matching lines @@
     // append() has special code paths for String backed StringView instead of
     // just char* backed ones.
     StringBuilder builder6;
     builder6.append(String("ghi"), 1, 2);
     expectBuilderContent("hi", builder6);
 
     // Test appending UChar32 characters to StringBuilder.
     StringBuilder builderForUChar32Append;
     UChar32 frakturAChar = 0x1D504;
     builderForUChar32Append.append(frakturAChar); // The fraktur A is not in the BMP, so it's two UTF-16 code units long.
+    EXPECT_FALSE(builderForUChar32Append.is8Bit());
     EXPECT_EQ(2U, builderForUChar32Append.length());
     builderForUChar32Append.append(static_cast<UChar32>('A'));
     EXPECT_EQ(3U, builderForUChar32Append.length());
     const UChar resultArray[] = { U16_LEAD(frakturAChar), U16_TRAIL(frakturAChar), 'A' };
     expectBuilderContent(String(resultArray, WTF_ARRAY_LENGTH(resultArray)), builderForUChar32Append);
 }
 
 TEST(StringBuilderTest, AppendSharingImpl)
 {
     String string("abc");
@@ skipping 105 matching lines @@
     builder2.toString(); // Test after reifyString().
     EXPECT_TRUE(builder1 != builder2);
 
     builder2.resize(3);
     EXPECT_TRUE(builder1 == builder2);
 
     builder1.toString(); // Test after reifyString().
     EXPECT_TRUE(builder1 == builder2);
 }
 
-TEST(StringBuilderTest, CanShrink)
-{
-    StringBuilder builder;
-    builder.reserveCapacity(256);
-    EXPECT_TRUE(builder.canShrink());
-    for (int i = 0; i < 256; i++)
-        builder.append('x');
-    EXPECT_EQ(builder.length(), builder.capacity());
-    EXPECT_FALSE(builder.canShrink());
-}
-
 TEST(StringBuilderTest, ToAtomicString)
 {
     StringBuilder builder;
     builder.append("123");
     AtomicString atomicString = builder.toAtomicString();
     EXPECT_EQ(String("123"), atomicString);
 
     builder.reserveCapacity(256);
-    EXPECT_TRUE(builder.canShrink());
     for (int i = builder.length(); i < 128; i++)
         builder.append('x');
     AtomicString atomicString1 = builder.toAtomicString();
     EXPECT_EQ(128u, atomicString1.length());
     EXPECT_EQ('x', atomicString1[127]);
 
     // Later change of builder should not affect the atomic string.
     for (int i = builder.length(); i < 256; i++)
         builder.append('x');
     EXPECT_EQ(128u, atomicString1.length());
 
-    EXPECT_FALSE(builder.canShrink());
     String string = builder.toString();
     AtomicString atomicString2 = builder.toAtomicString();
     // They should share the same StringImpl.
     EXPECT_EQ(atomicString2.impl(), string.impl());
 }
 
 TEST(StringBuilderTest, ToAtomicStringOnEmpty)
 {
     { // Default constructed.
         StringBuilder builder;
@@ skipping 62 matching lines @@
     StringBuilder reference;
     reference.append(replacementCharacter); // Make it UTF-16.
     reference.append(String::number(someNumber));
     StringBuilder test;
     test.append(replacementCharacter);
     test.appendNumber(someNumber);
     EXPECT_EQ(reference, test);
 }
 
 } // namespace WTF