added support for push_constant layout

src/sksl/SkSLParser.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
  
 #include "stdio.h"
 #include "SkSLParser.h"
 #include "SkSLToken.h"
@@ skipping 508 matching lines @@
     if (!this->expect(Token::EQ, "'='")) {
         return -1;
     }
     Token resultToken;
     if (this->expect(Token::INT_LITERAL, "a non-negative integer", &resultToken)) {
         return SkSL::stoi(resultToken.fText);
     }
     return -1;
 }
 
-/* LAYOUT LPAREN IDENTIFIER EQ INT_LITERAL (COMMA IDENTIFIER EQ INT_LITERAL)* 
-   RPAREN */
+/* LAYOUT LPAREN IDENTIFIER (EQ INT_LITERAL)? (COMMA IDENTIFIER (EQ INT_LITERAL)?)* RPAREN */
 ASTLayout Parser::layout() {
     int location = -1;
     int binding = -1;
     int index = -1;
     int set = -1;
     int builtin = -1;
     bool originUpperLeft = false;
     bool overrideCoverage = false;
     bool blendSupportAllEquations = false;
+    bool pushConstant = false;
     if (this->peek().fKind == Token::LAYOUT) {
         this->nextToken();
         if (!this->expect(Token::LPAREN, "'('")) {
             return ASTLayout(location, binding, index, set, builtin, originUpperLeft,
-                             overrideCoverage, blendSupportAllEquations);
+                             overrideCoverage, blendSupportAllEquations, pushConstant);
         }
         for (;;) {
             Token t = this->nextToken();
             if (t.fText == "location") {
                 location = this->layoutInt();
             } else if (t.fText == "binding") {
                 binding = this->layoutInt();
             } else if (t.fText == "index") {
                 index = this->layoutInt();
             } else if (t.fText == "set") {
                 set = this->layoutInt();
             } else if (t.fText == "builtin") {
                 builtin = this->layoutInt();
             } else if (t.fText == "origin_upper_left") {
                 originUpperLeft = true;
             } else if (t.fText == "override_coverage") {
                 overrideCoverage = true;
             } else if (t.fText == "blend_support_all_equations") {
                 blendSupportAllEquations = true;
+            } else if (t.fText == "push_constant") {
+                pushConstant = true;
             } else {
                 this->error(t.fPosition, ("'" + t.fText + 
                                           "' is not a valid layout qualifier").c_str());
             }
             if (this->peek().fKind == Token::RPAREN) {
                 this->nextToken();
                 break;
             }
             if (!this->expect(Token::COMMA, "','")) {
                 break;
             }
         }
     }
     return ASTLayout(location, binding, index, set, builtin, originUpperLeft, overrideCoverage,
-                     blendSupportAllEquations);
+                     blendSupportAllEquations, pushConstant);
 }
 
 /* layout? (UNIFORM | CONST | IN | OUT | INOUT | LOWP | MEDIUMP | HIGHP | FLAT | NOPERSPECTIVE)* */
 ASTModifiers Parser::modifiers() {
     ASTLayout layout = this->layout();
     int flags = 0;
     for (;;) {
         // TODO: handle duplicate / incompatible flags
         switch (peek().fKind) {
             case Token::UNIFORM:
@@ skipping 898 matching lines @@
 bool Parser::identifier(std::string* dest) {
     Token t;
     if (this->expect(Token::IDENTIFIER, "identifier", &t)) {
         *dest = t.fText; 
         return true;
     }
     return false;
 }
 
 } // namespace