added SkSL support for mustForceNegatedAtanParamToFloat cap

src/sksl/SkSLGLSLCodeGenerator.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_GLSLCODEGENERATOR
 #define SKSL_GLSLCODEGENERATOR
 
@@ skipping 37 matching lines @@
     int fVersion;
     enum {
         kGL_Standard,
         kGLES_Standard
     } fStandard;
     bool fIsCoreProfile;
     bool fUsesPrecisionModifiers;
     bool fMustDeclareFragmentShaderOutput;
     // The Tegra3 compiler will sometimes never return if we have min(abs(x), y)
     bool fCanUseMinAndAbsTogether;
+    // On Intel GPU there is an issue where it misinterprets an atan argument (second argument only,
+    // apparently) of the form "-<expr>" as an int, so we rewrite it as "-1.0 * <expr>" to avoid
+    // this problem
+    bool fMustForceNegatedAtanParamToFloat;
 };
 
 /**
  * Converts a Program into GLSL code.
  */
 class GLSLCodeGenerator : public CodeGenerator {
 public:
     enum Precedence {
         kParentheses_Precedence    =  1,
         kPostfix_Precedence        =  2,
@@ skipping 112 matching lines @@
     bool fAtLineStart;
     // Keeps track of which struct types we have written. Given that we are unlikely to ever write 
     // more than one or two structs per shader, a simple linear search will be faster than anything 
     // fancier.
     std::vector<const Type*> fWrittenStructs;
 };
 
 }
 
 #endif