Add gl_SampleMask functionality to fragment builders

src/gpu/glsl/GrGLSL.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSL_DEFINED
 #define GrGLSL_DEFINED
 
@@ skipping 19 matching lines @@
     k140_GrGLSLGeneration,
     /**
      * Desktop GLSL 1.50
      */
     k150_GrGLSLGeneration,
     /**
      * Desktop GLSL 3.30, and ES GLSL 3.00
      */
     k330_GrGLSLGeneration,
     /**
+     * Desktop GLSL 4.00
+     */
+    k400_GrGLSLGeneration,
+    /**
      * ES GLSL 3.10 only TODO Make GLSLCap objects to make this more granular
      */
     k310es_GrGLSLGeneration,
+    /**
+     * ES GLSL 3.20
+     */
+    k320es_GrGLSLGeneration,
 };
 
 bool GrGLSLSupportsNamedFragmentShaderOutputs(GrGLSLGeneration);
 
 /**
  * Gets the name of the function that should be used to sample a 2D texture. Coord type is used
  * to indicate whether the texture is sampled using projective textured (kVec3f) or not (kVec2f).
  */
 inline const char* GrGLSLTexture2DFunctionName(GrSLType coordType, GrSLType samplerType,
                                                GrGLSLGeneration glslGen) {
@@ skipping 52 matching lines @@
         case kInt_GrSLType:
             return "int";
         case kUint_GrSLType:
             return "uint";
         default:
             SkFAIL("Unknown shader var type.");
             return ""; // suppress warning
     }
 }
 
+/**
+ * Returns the minimum precision that can fully represent an int with the provided number of bits.
+ */
+static inline GrSLPrecision GrGLSLIntMinPrecisionForNBits(int bits) {

[bsalomon, 2016/02/12 20:58:17]

If we're not using this can we remove it?

[Chris Dalton, 2016/02/12 21:01:50]

Oops. Done.

+    SkASSERT(bits <= 32);
+    if (bits <= 9) { // Lowp integers are spec'd to have at least 9 bits.
+        return kLow_GrSLPrecision;
+    } else if (bits <= 16) {
+        return kMedium_GrSLPrecision;
+    } else {
+        return kHigh_GrSLPrecision;
+    }
+}
+
 /** A generic base-class representing a GLSL expression.
  * The instance can be a variable name, expression or vecN(0) or vecN(1). Does simple constant
  * folding with help of 1 and 0.
  *
  * Clients should not use this class, rather the specific instantiations defined
  * later, for example GrGLSLExpr4.
  */
 template <typename Self>
 class GrGLSLExpr {
 public:
@@ skipping 222 matching lines @@
 
 /**
  * Does an inplace mul, *=, of vec4VarName by mulFactor.
  * A semicolon is added after the assignment.
  */
 void GrGLSLMulVarBy4f(SkString* outAppend, const char* vec4VarName, const GrGLSLExpr4& mulFactor);
 
 #include "GrGLSL_impl.h"
 
 #endif