LibJS: Partially implement resizable ArrayBuffer objects

This is (part of) a normative change in the ECMA-262 spec. See:
a9ae96e

This implements just support for resizing ArrayBuffer objects. This does
not implement the SharedArrayBuffer changes, as we do not have enough
support to do so.

Userland/Libraries/LibJS/Tests/builtins/ArrayBuffer/ArrayBuffer.js

@@ -17,3 +17,18 @@ test("ArrayBuffer size limit", () => {
         new ArrayBuffer(2 ** 53);
     }).toThrowWithMessage(RangeError, "Invalid array buffer length");
 });
+
+test("invalid ArrayBuffer maximum size option", () => {
+    expect(() => {
+        new ArrayBuffer(10, { maxByteLength: -1 });
+    }).toThrowWithMessage(RangeError, "Index must be a positive integer");
+});
+
+test("ArrayBuffer size exceeds maximum size", () => {
+    expect(() => {
+        new ArrayBuffer(10, { maxByteLength: 5 });
+    }).toThrowWithMessage(
+        RangeError,
+        "ArrayBuffer byte length of 10 exceeds the max byte length of 5"
+    );
+});

Userland/Libraries/LibJS/Tests/builtins/ArrayBuffer/ArrayBuffer.prototype.maxByteLength.js

@@ -0,0 +1,29 @@
+describe("errors", () => {
+    test("called on non-ArrayBuffer object", () => {
+        expect(() => {
+            ArrayBuffer.prototype.maxByteLength;
+        }).toThrowWithMessage(TypeError, "Not an object of type ArrayBuffer");
+    });
+});
+
+describe("normal behavior", () => {
+    test("detached buffer", () => {
+        let buffer = new ArrayBuffer(5);
+        detachArrayBuffer(buffer);
+        expect(buffer.maxByteLength).toBe(0);
+
+        buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+        detachArrayBuffer(buffer);
+        expect(buffer.maxByteLength).toBe(0);
+    });
+
+    test("fixed buffer", () => {
+        let buffer = new ArrayBuffer(5);
+        expect(buffer.maxByteLength).toBe(5);
+    });
+
+    test("resizable buffer", () => {
+        let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+        expect(buffer.maxByteLength).toBe(10);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/ArrayBuffer/ArrayBuffer.prototype.resizable.js

@@ -0,0 +1,19 @@
+describe("errors", () => {
+    test("called on non-ArrayBuffer object", () => {
+        expect(() => {
+            ArrayBuffer.prototype.resizable;
+        }).toThrowWithMessage(TypeError, "Not an object of type ArrayBuffer");
+    });
+});
+
+describe("normal behavior", () => {
+    test("fixed buffer", () => {
+        let buffer = new ArrayBuffer(5);
+        expect(buffer.resizable).toBeFalse();
+    });
+
+    test("resizable buffer", () => {
+        let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+        expect(buffer.resizable).toBeTrue();
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/ArrayBuffer/ArrayBuffer.prototype.resize.js

@@ -0,0 +1,57 @@
+describe("errors", () => {
+    test("called on non-ArrayBuffer object", () => {
+        expect(() => {
+            ArrayBuffer.prototype.resize(10);
+        }).toThrowWithMessage(TypeError, "Not an object of type ArrayBuffer");
+    });
+
+    test("fixed buffer", () => {
+        let buffer = new ArrayBuffer(5);
+        detachArrayBuffer(buffer);
+
+        expect(() => {
+            buffer.resize(10);
+        }).toThrowWithMessage(TypeError, "ArrayBuffer is not resizable");
+    });
+
+    test("detached buffer", () => {
+        let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+        detachArrayBuffer(buffer);
+
+        expect(() => {
+            buffer.resize(10);
+        }).toThrowWithMessage(TypeError, "ArrayBuffer is detached");
+    });
+
+    test("invalid new byte length", () => {
+        let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+
+        expect(() => {
+            buffer.resize(-1);
+        }).toThrowWithMessage(RangeError, "Index must be a positive integer");
+    });
+
+    test("new byte length exceeds maximum size", () => {
+        let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+
+        expect(() => {
+            buffer.resize(11);
+        }).toThrowWithMessage(
+            RangeError,
+            "ArrayBuffer byte length of 11 exceeds the max byte length of 10"
+        );
+    });
+});
+
+describe("normal behavior", () => {
+    test("resizable buffer", () => {
+        let buffer = new ArrayBuffer(5, { maxByteLength: 10 });
+        expect(buffer.byteLength).toBe(5);
+        expect(buffer.maxByteLength).toBe(10);
+
+        for (let i = 0; i <= buffer.maxByteLength; ++i) {
+            buffer.resize(i);
+            expect(buffer.byteLength).toBe(i);
+        }
+    });
+});