added initial GLSL support to skslc

src/sksl/ir/SkSLLayout.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
  
 #ifndef SKSL_LAYOUT
 #define SKSL_LAYOUT
 
 namespace SkSL {
 
 /**
  * Represents a layout block appearing before a variable declaration, as in:
  *
  * layout (location = 0) int x;
  */
 struct Layout {
     Layout(const ASTLayout& layout)
     : fLocation(layout.fLocation)
     , fBinding(layout.fBinding)
     , fIndex(layout.fIndex)
     , fSet(layout.fSet)
-    , fBuiltin(layout.fBuiltin) {}
+    , fBuiltin(layout.fBuiltin)
+    , fOriginUpperLeft(layout.fOriginUpperLeft) {}
 
-    Layout(int location, int binding, int index, int set, int builtin)
+    Layout(int location, int binding, int index, int set, int builtin, bool originUpperLeft)
     : fLocation(location)
     , fBinding(binding)
     , fIndex(index)
     , fSet(set)
-    , fBuiltin(builtin) {}
+    , fBuiltin(builtin)
+    , fOriginUpperLeft(originUpperLeft) {}
 
     std::string description() const {
         std::string result;
         std::string separator;
         if (fLocation >= 0) {
             result += separator + "location = " + to_string(fLocation);
             separator = ", ";
         }
         if (fBinding >= 0) {
             result += separator + "binding = " + to_string(fBinding);
             separator = ", ";
         }
         if (fIndex >= 0) {
             result += separator + "index = " + to_string(fIndex);
             separator = ", ";
         }
         if (fSet >= 0) {
             result += separator + "set = " + to_string(fSet);
             separator = ", ";
         }
         if (fBuiltin >= 0) {
             result += separator + "builtin = " + to_string(fBuiltin);
             separator = ", ";
         }
+        if (fOriginUpperLeft) {
+            result += separator + "origin_upper_left";
+            separator = ", ";
+        }
         if (result.length() > 0) {
             result = "layout (" + result + ")";
         }
         return result;
     }
 
     bool operator==(const Layout& other) const {
         return fLocation == other.fLocation &&
                fBinding  == other.fBinding &&
                fIndex    == other.fIndex &&
                fSet      == other.fSet &&
                fBuiltin  == other.fBuiltin;
     }
 
     bool operator!=(const Layout& other) const {
         return !(*this == other);
     }
 
-    const int fLocation;
-    const int fBinding;
-    const int fIndex;
-    const int fSet;
-    const int fBuiltin;
+    // everything but builtin is in the GLSL spec; builtin comes from SPIR-V and identifies which
+    // particular builtin value this object represents.
+    int fLocation;
+    int fBinding;
+    int fIndex;
+    int fSet;
+    int fBuiltin;
+    bool fOriginUpperLeft;
 };
 
 } // namespace
 
 #endif