Revert of [parser] Forbid \08 in strict strings (patchset #3 id:40001 of...

Revert of [parser] Forbid \08 in strict strings (patchset #3 id:40001 of https://codereview.chromium.org/2950633002/ )

Reason for revert:
Breaks layout test:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/16403

See:
https://github.com/v8/v8/wiki/Blink-layout-tests

Original issue's description:
> [parser] Forbid \08 in strict strings and in untagged templates
>
> This was never legal; the spec only allows '\0' in strict-mode strings or templates
> when not followed by a decimal digit. Previously we were only enforcing that it
> not be followed by an _octal_ digit.
>
> This was already fixed for numeric literals, but not for escape sequences in strings.
>
> BUG=v8:6504
>
> Review-Url: https://codereview.chromium.org/2950633002
> Cr-Commit-Position: refs/heads/master@{#46046}
> Committed: https://chromium.googlesource.com/v8/v8/+/b102540e44a72157098014a20399193a461153d2

TBR=vogelheim@chromium.org,bakkot@gmail.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:6504

Review-Url: https://codereview.chromium.org/2946953002
Cr-Commit-Position: refs/heads/master@{#46068}

src/parsing/scanner.cc

@@ -1032,7 +1032,7 @@ uc32 Scanner::ScanOctalEscape(uc32 c, int length) {
   // can be reported later (in strict mode).
   // We don't report the error immediately, because the octal escape can
   // occur before the "use strict" directive.
-  if (c != '0' || i > 0 || c0_ == '8' || c0_ == '9') {
+  if (c != '0' || i > 0) {
     octal_pos_ = Location(source_pos() - i - 1, source_pos() - 1);
     octal_message_ = MessageTemplate::kStrictOctalEscape;
   }

test/cctest/test-parsing.cc

@@ -5901,33 +5901,6 @@ TEST(UnicodeEscapes) {
   RunParserSyncTest(context_data, data, kSuccess);
 }
 
-TEST(OctalEscapes) {
-  const char* sloppy_context_data[][2] = {{"", ""},    // as a directive
-                                          {"0;", ""},  // as a string literal
-                                          {NULL, NULL}};
-
-  const char* strict_context_data[][2] = {
-      {"'use strict';", ""},     // as a directive before 'use strict'
-      {"", ";'use strict';"},    // as a directive after 'use strict'
-      {"'use strict'; 0;", ""},  // as a string literal
-      {NULL, NULL}};
-
-  // clang-format off
-  const char* data[] = {
-    "'\\1'",
-    "'\\01'",
-    "'\\001'",
-    "'\\08'",
-    "'\\09'",
-    NULL};
-  // clang-format on
-
-  // Permitted in sloppy mode
-  RunParserSyncTest(sloppy_context_data, data, kSuccess);
-
-  // Error in strict mode
-  RunParserSyncTest(strict_context_data, data, kError);
-}
 
 TEST(ScanTemplateLiterals) {
   const char* context_data[][2] = {{"'use strict';", ""},
@@ -7139,7 +7112,6 @@ TEST(TemplateEscapesPositiveTests) {
 
   // clang-format off
   const char* data[] = {
-    "tag`\\08`",
     "tag`\\01`",
     "tag`\\01${0}right`",
     "tag`left${0}\\01`",
@@ -7223,7 +7195,6 @@ TEST(TemplateEscapesNegativeTests) {
 
   // clang-format off
   const char* data[] = {
-    "`\\08`",
     "`\\01`",
     "`\\01${0}right`",
     "`left${0}\\01`",

test/mjsunit/es6/templates.js

@@ -476,7 +476,7 @@ var obj = {
 (function testLegacyOctal() {
   assertEquals('\u0000', `\0`);
   assertEquals('\u0000a', `\0a`);
-  for (var i = 0; i < 10; i++) {
+  for (var i = 0; i < 8; i++) {
     var code = "`\\0" + i + "`";
     assertThrows(code, SyntaxError);
     code = "(function(){})" + code;
@@ -502,6 +502,8 @@ var obj = {
 (function testValidNumericEscapes() {
   assertEquals("8", `\8`);
   assertEquals("9", `\9`);
+  assertEquals("\u00008", `\08`);
+  assertEquals("\u00009", `\09`);
 })();