Revert of added support for push_constant layout

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"
 
-#if SK_SUPPORT_GPU
+#if SKIA_SUPPORT_GPU
 
 static void test(skiatest::Reporter* r, const char* src, const GrGLSLCaps& 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);
@@ skipping 494 matching lines @@
          "    int x;\n"
          "    x = 1;\n"
          "    x = 2;\n"
          "    x = 5;\n"
          "    {\n"
          "    }\n"
          "}\n");
 }
 
 #endif