Reduced skslc memory consumption

src/sksl/ir/SkSLType.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 SKIASL_TYPE
 #define SKIASL_TYPE
 
@@ skipping 39 matching lines @@
         kSampler_Kind,
         kOther_Kind
     };
 
     // Create an "other" (special) type with the given name. These types cannot be directly 
     // referenced from user code.
     Type(std::string name)
     : INHERITED(Position(), kType_Kind, std::move(name))
     , fTypeKind(kOther_Kind) {}
 
-    // Create a generic type which maps to the listed types.
+    // Create a generic type which maps to the listed types. As currently implemented, there are 
+    // always exactly four coercion targets, mapping to the scalar, vec2, vec3, and vec4 versions of 
+    // a type.
     Type(std::string name, std::vector<const Type*> types)
     : INHERITED(Position(), kType_Kind, std::move(name))
     , fTypeKind(kGeneric_Kind)
     , fCoercibleTypes(std::move(types)) {
         ASSERT(fCoercibleTypes.size() == 4);
     }
 
     // Create a struct type with the given fields.
     Type(std::string name, std::vector<Field> fields)
     : INHERITED(Position(), kType_Kind, std::move(name))
@@ skipping 265 matching lines @@
     const SpvDim_ fDimensions = SpvDim1D;
     const bool fIsDepth = false;
     const bool fIsArrayed = false;
     const bool fIsMultisampled = false;
     const bool fIsSampled = false;
 };
 
 } // namespace
 
 #endif