[regexp] Rename result.group to result.groups

This is just an update to reflect the current spec proposal.
https://tc39.github.io/proposal-regexp-named-groups/

BUG=v8:5437

Review-Url: https://codereview.chromium.org/2769143002
Cr-Commit-Position: refs/heads/master@{#44067}

src/builtins/builtins-regexp-gen.cc

@@ -165,7 +165,7 @@ Node* RegExpBuiltinsAssembler::ConstructNewResultFromMatchInfo(
     // Store it on the result as a 'group' property.
 
     {
-      Node* const name = HeapConstant(isolate()->factory()->group_string());
+      Node* const name = HeapConstant(isolate()->factory()->groups_string());
       CallRuntime(Runtime::kCreateDataProperty, context, result, name,
                   group_object);
     }

src/heap-symbols.h

@@ -80,7 +80,7 @@
   V(get_string, "get")                                             \
   V(get_space_string, "get ")                                      \
   V(global_string, "global")                                       \
-  V(group_string, "group")                                         \
+  V(groups_string, "groups")                                       \
   V(has_string, "has")                                             \
   V(hour_string, "hour")                                           \
   V(ignoreCase_string, "ignoreCase")                               \

test/mjsunit/harmony/regexp-named-captures.js

@@ -76,23 +76,23 @@ assertEquals(["bab", "b"], "bab".match(/\k<a>(?<a>b)\w\k<a>/u));
 assertEquals(["bab", "b", "a"], "bab".match(/(?<b>b)\k<a>(?<a>a)\k<b>/u));
 
 // Reference properties.
-assertEquals("a", /(?<a>a)(?<b>b)\k<a>/u.exec("aba").group.a);
-assertEquals("b", /(?<a>a)(?<b>b)\k<a>/u.exec("aba").group.b);
-assertEquals(undefined, /(?<a>a)(?<b>b)\k<a>/u.exec("aba").group.c);
-assertEquals(undefined, /(?<a>a)(?<b>b)\k<a>|(?<c>c)/u.exec("aba").group.c);
+assertEquals("a", /(?<a>a)(?<b>b)\k<a>/u.exec("aba").groups.a);
+assertEquals("b", /(?<a>a)(?<b>b)\k<a>/u.exec("aba").groups.b);
+assertEquals(undefined, /(?<a>a)(?<b>b)\k<a>/u.exec("aba").groups.c);
+assertEquals(undefined, /(?<a>a)(?<b>b)\k<a>|(?<c>c)/u.exec("aba").groups.c);
 
 // Unicode names.
-assertEquals("a", /(?<π>a)/u.exec("bab").group.π);
-assertEquals("a", /(?<\u{03C0}>a)/u.exec("bab").group.\u03C0);
-assertEquals("a", /(?<$>a)/u.exec("bab").group.$);
-assertEquals("a", /(?<_>a)/u.exec("bab").group._);
-assertEquals("a", /(?<$𐒤>a)/u.exec("bab").group.$𐒤);
-assertEquals("a", /(?<_\u200C>a)/u.exec("bab").group._\u200C);
-assertEquals("a", /(?<_\u200D>a)/u.exec("bab").group._\u200D);
-assertEquals("a", /(?<ಠ_ಠ>a)/u.exec("bab").group.ಠ_ಠ);
+assertEquals("a", /(?<π>a)/u.exec("bab").groups.π);
+assertEquals("a", /(?<\u{03C0}>a)/u.exec("bab").groups.\u03C0);
+assertEquals("a", /(?<$>a)/u.exec("bab").groups.$);
+assertEquals("a", /(?<_>a)/u.exec("bab").groups._);
+assertEquals("a", /(?<$𐒤>a)/u.exec("bab").groups.$𐒤);
+assertEquals("a", /(?<_\u200C>a)/u.exec("bab").groups._\u200C);
+assertEquals("a", /(?<_\u200D>a)/u.exec("bab").groups._\u200D);
+assertEquals("a", /(?<ಠ_ಠ>a)/u.exec("bab").groups.ಠ_ಠ);
 assertThrows('/(?<❤>a)/u', SyntaxError);
 assertThrows('/(?<𐒤>a)/u', SyntaxError);  // ID_Continue but not ID_Start.
 
 // The '__proto__' property on the groups object.
-assertEquals(undefined, /(?<a>.)/u.exec("a").group.__proto__);
-assertEquals("a", /(?<__proto__>a)/u.exec("a").group.__proto__);
+assertEquals(undefined, /(?<a>.)/u.exec("a").groups.__proto__);
+assertEquals("a", /(?<__proto__>a)/u.exec("a").groups.__proto__);