added SkSL support for mustForceNegatedAtanParamToFloat cap

src/gpu/gl/builders/GrGLShaderStringBuilder.cpp

Index: src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
diff --git a/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp b/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
index b26ce894f0246b35dbf6a0ecfcb266a89eedda43..8e8bb9a0fc15427c29795fd94f4b66cc833747e4 100644
--- a/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLShaderStringBuilder.cpp
@@ -86,6 +86,7 @@ SkSL::GLCaps GrGLSkSLCapsForContext(const GrGLContext& context) {
     result.fUsesPrecisionModifiers = glslCaps->usesPrecisionModifiers();
     result.fMustDeclareFragmentShaderOutput = glslCaps->mustDeclareFragmentShaderOutput();
     result.fCanUseMinAndAbsTogether = glslCaps->canUseMinAndAbsTogether();
+    result.fMustForceNegatedAtanParamToFloat = glslCaps->mustForceNegatedAtanParamToFloat();
     return result;
 }