Implement Wasm binding for Tree.getChangedRanges()

lib/binding_web/test/tree-test.js

@@ -81,6 +81,54 @@ describe("Tree", () => {
     });
   });
 
+  describe(".getChangedRanges(previous)", () => {
+    it("reports the ranges of text whose syntactic meaning has changed", () => {
+      let sourceCode = "abcdefg + hij";
+      tree = parser.parse(sourceCode);
+
+      assert.equal(
+        tree.rootNode.toString(),
+        "(program (expression_statement (binary_expression (identifier) (identifier))))"
+      );
+
+      sourceCode = "abc + defg + hij";
+      tree.edit({
+        startIndex: 2,
+        oldEndIndex: 2,
+        newEndIndex: 5,
+        startPosition: { row: 0, column: 2 },
+        oldEndPosition: { row: 0, column: 2 },
+        newEndPosition: { row: 0, column: 5 }
+      });
+
+      const tree2 = parser.parse(sourceCode, tree);
+      assert.equal(
+        tree2.rootNode.toString(),
+        "(program (expression_statement (binary_expression (binary_expression (identifier) (identifier)) (identifier))))"
+      );
+
+      const ranges = tree.getChangedRanges(tree2);
+      assert.deepEqual(ranges, [
+        {
+          startIndex: 0,
+          endIndex: "abc + defg".length,
+          startPosition: { row: 0, column: 0 },
+          endPosition: { row: 0, column: "abc + defg".length }
+        }
+      ]);
+
+      tree2.delete();
+    });
+
+    it('throws an exception if the argument is not a tree', () => {
+      tree = parser.parse("abcdefg + hij");
+
+      assert.throws(() => {
+        tree.getChangedRanges({});
+      }, /Argument must be a Tree/);
+    })
+  });
+
   describe(".walk()", () => {
     let cursor