[parser] Turn on --harmony-template-escapes by default

This flag allows invalid escape sequences in tagged templates, which is
a stage-4 TC39 proposal shipping in other browsers.

Bug: v8:5546
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I3e7c374c9b547f62d5976f76a7208d05fe9decf8
Reviewed-on: https://chromium-review.googlesource.com/581885
Commit-Queue: Kevin Gibbons <bakkot@gmail.com>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47584}

src/flag-definitions.h

@@ -211,8 +211,6 @@ DEFINE_IMPLICATION(es_staging, harmony)
   V(harmony_function_tostring, "harmony Function.prototype.toString")   \
   V(harmony_regexp_named_captures, "harmony regexp named captures")     \
   V(harmony_regexp_property, "harmony Unicode regexp property classes") \
-  V(harmony_template_escapes,                                           \
-    "harmony invalid escapes in tagged template literals")              \
   V(harmony_restrict_constructor_return,                                \
     "harmony disallow non undefined primitive return value from class " \
     "constructor")                                                      \
@@ -228,7 +226,9 @@ DEFINE_IMPLICATION(es_staging, harmony)
   V(harmony_object_rest_spread, "harmony object rest spread properties") \
   V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")              \
   V(harmony_regexp_dotall, "harmony regexp dotAll flag")                 \
-  V(harmony_regexp_lookbehind, "harmony regexp lookbehind")
+  V(harmony_regexp_lookbehind, "harmony regexp lookbehind")              \
+  V(harmony_template_escapes,                                            \
+    "harmony invalid escapes in tagged template literals")
 
 // Once a shipping feature has proved stable in the wild, it will be dropped
 // from HARMONY_SHIPPING, all occurrences of the FLAG_ variable are removed,

test/message/regress/regress-4829-1.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --no-harmony-template-escapes
+
 function tag() {}
 
 tag(tag`\xyy`);

test/message/regress/regress-4829-1.out

@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-*%(basename)s:7: SyntaxError: Invalid hexadecimal escape sequence
+*%(basename)s:9: SyntaxError: Invalid hexadecimal escape sequence
 tag(tag`\xyy`);
         ^^^^
 SyntaxError: Invalid hexadecimal escape sequence

test/message/regress/regress-4829-2.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --no-harmony-template-escapes
+
 function tag() {}
 
 `${tag`\xyy`}`;

test/message/regress/regress-4829-2.out

@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-*%(basename)s:7: SyntaxError: Invalid hexadecimal escape sequence
+*%(basename)s:9: SyntaxError: Invalid hexadecimal escape sequence
 `${tag`\xyy`}`;
        ^^^^
 SyntaxError: Invalid hexadecimal escape sequence

test/mjsunit/es6/templates.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --no-harmony-template-escapes
+
 var num = 5;
 var str = "str";
 function fn() { return "result"; }