re-re-land of skslc now automatically turns on derivatives support

tests/SkSLGLSLTest.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSLCompiler.h"
 
 #include "Test.h"
 
 static void test(skiatest::Reporter* r, const char* src, SkSL::GLCaps caps, const char* expected) {
     SkSL::Compiler compiler;
     std::string output;
     bool result = compiler.toGLSL(SkSL::Program::kFragment_Kind, src, caps, &output);
     if (!result) {
         SkDebugf("Unexpected error compiling %s\n%s", src, compiler.errorText().c_str());
     }
     REPORTER_ASSERT(r, result);
     if (result) {
         if (output != expected) {
             SkDebugf("GLSL MISMATCH:\nsource:\n%s\n\nexpected:\n'%s'\n\nreceived:\n'%s'", src, 
                      expected, output.c_str());
         }
         REPORTER_ASSERT(r, output == expected);
     }
 }
 
 static SkSL::GLCaps default_caps() {
-    return { 
-             400, 
-             SkSL::GLCaps::kGL_Standard,
-             false, // isCoreProfile
-             false, // usesPrecisionModifiers;
-             false, // mustDeclareFragmentShaderOutput
-             true,  // canUseMinAndAbsTogether
-             false  // mustForceNegatedAtanParamToFloat
-           };
+    return SkSL::GLCaps();
 }
 
 DEF_TEST(SkSLHelloWorld, r) {
     test(r,
          "void main() { sk_FragColor = vec4(0.75); }",
          default_caps(),
          "#version 400\n"
          "void main() {\n"
          "    gl_FragColor = vec4(0.75);\n"
          "}\n");
@@ skipping 331 matching lines @@
     test(r,
          "float test1[] = float[](1, 2, 3, 4);"
          "vec2 test2[] = vec2[](vec2(1, 2), vec2(3, 4));"
          "mat4 test3[] = mat4[]();",
          default_caps(),
          "#version 400\n"
          "float test1[] = float[](1.0, 2.0, 3.0, 4.0);\n"
          "vec2 test2[] = vec2[](vec2(1.0, 2.0), vec2(3.0, 4.0));\n"
          "mat4 test3[] = mat4[]();\n");
 }
+
+DEF_TEST(SkSLDerivatives, r) {
+    test(r,
+         "void main() { float x = dFdx(1); }",
+         default_caps(),
+         "#version 400\n"
+         "void main() {\n"
+         "    float x = dFdx(1.0);\n"
+         "}\n");
+    SkSL::GLCaps caps = default_caps();
+    caps.fShaderDerivativeExtensionString = "GL_OES_standard_derivatives";
+    test(r,
+         "void main() { float x = 1; }",
+         caps,
+         "#version 400\n"
+         "void main() {\n"
+         "    float x = 1.0;\n"
+         "}\n");
+    test(r,
+         "void main() { float x = dFdx(1); }",
+         caps,
+         "#version 400\n"
+         "#extension GL_OES_standard_derivatives : require\n"
+         "void main() {\n"
+         "    float x = dFdx(1.0);\n"
+         "}\n");
+}