Fixed a broken StackMapTable.

[tuchida]

Before the fix, I got this error when I ran the test.

org.mozilla.javascript.classfile.tests.ClassFileWriterTest > testStackMapTable FAILED
    java.lang.VerifyError: Inconsistent stackmap frames at branch target 34
    Exception Details:
      Location:
        TestStackMapTable.returnObject()Ljava/lang/Object; @34: aload_0
      Reason:
        Type 'java/math/BigInteger' (current frame, stack[0]) is not assignable to 'TestStackMapTable' (stack map, stack[0])
      Current Frame:
        bci: @27
        flags: { }
        locals: { '[Z' }
        stack: { 'java/math/BigInteger' }
      Stackmap Frame:
        bci: @34
        flags: { }
        locals: { '[Z' }
        stack: { 'TestStackMapTable' }
      Bytecode:
        0x0000000: b800 164b bb00 0959 04bc 0859 0310 7b54
        0x0000010: b700 0d59 c700 0a2a 0304 54a7 0007 2a04
        0x0000020: 0454 2a05 0454 b0                      
      Stackmap Table:
        full_frame(@30,{Object[#24]},{Object[#9]})
        same_locals_1_stack_item_frame(@34,Object[#2])
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
        at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
        at java.lang.Class.getMethod0(Class.java:3018)
        at java.lang.Class.getMethod(Class.java:1784)
        at org.mozilla.javascript.classfile.tests.ClassFileWriterTest.testStackMapTable(ClassFileWriterTest.java:55)

---

rhino/src/org/mozilla/classfile/ClassFileWriter.java

Lines 2176 to 2181 in 1f45c8f

	if (tag == TypeInfo.UNINITIALIZED_VARIABLE(0) ||
	tag == TypeInfo.UNINITIALIZED_THIS) {
	if ("<init>".equals(methodName)) {
	int newType =
	TypeInfo.OBJECT(itsThisClassIndex);
	initializeTypeInfo(instType, newType);

UNINITIALIZED_THIS

example:

// constructor
public TestClass() {
    super();

It is correct to rewrite the UNINITIALIZED_THIS type with this.getClass() in this case.

UNINITIALIZED_VARIABLE(0)

example:

    o = new BigInteger(bytes);

It is probably correct to rewrite it with BigInteger instead of this.getClass() in this case.

I'm not familiar with Java bytecode, so could you please check if the pull request is correct?

[gbrail]

I'm all for fixing bugs at this layer and also having unit tests for it. Thanks!