path: fix win32 parse()

Fix path.win32.parse("/foo/bar") retuns `{root: '' ...}`(v5.7.0),
but not `{root: '/' ...}`(v5.6.0).

PR-URL: #5484
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Roman Reiss <me@silverwind.io>

Conflicts:
	test/parallel/test-path-parse-format.js

Author: zbinlin

lib/path.js

@@ -1007,8 +1007,8 @@ const win32 = {
         isAbsolute = true;
 
         code = path.charCodeAt(1);
+        rootEnd = 1;
         if (code === 47/*/*/ || code === 92/*\*/) {
-          rootEnd = 1;
           // Matched double path separator at beginning
           var j = 2;
           var last = j;

test/parallel/test-path-parse-format.js

@@ -19,7 +19,11 @@ var winPaths = [
   '\\\\?\\UNC\\server\\share'
 ];
 
-var winSpecialCaseFormatTests = [
+const winSpecialCaseParseTests = [
+  ['/foo/bar', {root: '/'}]
+];
+
+const winSpecialCaseFormatTests = [
   [{dir: 'some\\dir'}, 'some\\dir\\'],
   [{base: 'index.html'}, 'index.html'],
   [{}, '']
@@ -77,6 +81,7 @@ var errors = [
 
 checkParseFormat(path.win32, winPaths);
 checkParseFormat(path.posix, unixPaths);
+checkSpecialCaseParseFormat(path.win32, winSpecialCaseParseTests);
 checkErrors(path.win32);
 checkErrors(path.posix);
 checkFormat(path.win32, winSpecialCaseFormatTests);
@@ -175,6 +180,17 @@ function checkParseFormat(path, paths) {
   });
 }
 
+function checkSpecialCaseParseFormat(path, testCases) {
+  testCases.forEach(function(testCase) {
+    const element = testCase[0];
+    const expect = testCase[1];
+    const output = path.parse(element);
+    Object.keys(expect).forEach(function(key) {
+      assert.strictEqual(output[key], expect[key]);
+    });
+  });
+}
+
 function checkFormat(path, testCases) {
   testCases.forEach(function(testCase) {
     assert.strictEqual(path.format(testCase[0]), testCase[1]);