Remove meta viewport and @viewport CSS rules.

sky/engine/core/css/parser/CSSGrammar.y

Index: sky/engine/core/css/parser/CSSGrammar.y
diff --git a/sky/engine/core/css/parser/CSSGrammar.y b/sky/engine/core/css/parser/CSSGrammar.y
index 4ebae3cb31b881fa43353eef359f94209ffe739e..41fd5d49b7bfec17274ab554924bc8e503ba44ed 100644
--- a/sky/engine/core/css/parser/CSSGrammar.y
+++ b/sky/engine/core/css/parser/CSSGrammar.y
@@ -177,7 +177,6 @@ inline static CSSParserValue makeIdentValue(CSSParserString string)
 %token SUPPORTS_SYM
 %token FONT_FACE_SYM
 %token CHARSET_SYM
-%token VIEWPORT_RULE_SYM
 %token INTERNAL_DECLS_SYM
 %token INTERNAL_MEDIALIST_SYM
 %token INTERNAL_RULE_SYM
@@ -252,7 +251,6 @@ inline static CSSParserValue makeIdentValue(CSSParserString string)
 %type <rule> block_rule
 %type <rule> block_valid_rule
 %type <rule> supports
-%type <rule> viewport
 %type <boolean> keyframes_rule_start
 
 %type <string> ident_or_string
@@ -453,7 +451,6 @@ valid_rule:
   | font_face
   | keyframes
   | supports
-  | viewport
   ;
 
 before_rule:
@@ -498,7 +495,6 @@ block_valid_rule:
   | media
   | keyframes
   | supports
-  | viewport
   ;
 
 block_rule:
@@ -832,21 +828,6 @@ font_face:
     }
     ;
 
-before_viewport_rule:
-    /* empty */ {
-        parser->markViewportRuleBodyStart();
-        parser->startRuleHeader(CSSRuleSourceData::VIEWPORT_RULE);
-    }
-    ;
-
-viewport:
-    before_viewport_rule VIEWPORT_RULE_SYM at_rule_header_end_maybe_space
-    '{' at_rule_body_start maybe_space_before_declaration declaration_list closing_brace {
-        $$ = parser->createViewportRule();
-        parser->markViewportRuleBodyEnd();
-    }
-;
-
 maybe_unary_operator:
     unary_operator
     | /* empty */ { $$ = 1; }
@@ -1444,9 +1425,6 @@ regular_invalid_at_rule_header:
         parser->reportError($4, InvalidSupportsConditionCSSError);
         parser->popSupportsRuleData();
     }
-  | before_viewport_rule VIEWPORT_RULE_SYM at_rule_header_recovery {
-        parser->markViewportRuleBodyEnd();
-    }
   | error_location invalid_at at_rule_header_recovery {
         parser->resumeErrorLogging();
         parser->reportError($1, InvalidRuleCSSError);