SPV: Further refine OpenGL vs. Vulkan differences for SPIR-V.

Includes adding test cases to verify the differences.

gtests/Spv.FromFile.cpp

@@ -44,6 +44,7 @@ namespace {
 using CompileVulkanToSpirvTest = GlslangTest<::testing::TestWithParam<std::string>>;
 using CompileOpenGLToSpirvTest = GlslangTest<::testing::TestWithParam<std::string>>;
 using VulkanSemantics = GlslangTest<::testing::TestWithParam<std::string>>;
+using OpenGLSemantics = GlslangTest<::testing::TestWithParam<std::string>>;
 using VulkanAstSemantics = GlslangTest<::testing::TestWithParam<std::string>>;
 
 // Compiling GLSL to SPIR-V under Vulkan semantics. Expected to successfully
@@ -73,6 +74,15 @@ TEST_P(VulkanSemantics, FromFile)
                             Target::Spv);
 }
 
+// GLSL-level Vulkan semantics test. Expected to error out before generating
+// SPIR-V.
+TEST_P(OpenGLSemantics, FromFile)
+{
+    loadFileCompileAndCheck(GLSLANG_TEST_DIRECTORY, GetParam(),
+                            Source::GLSL, Semantics::OpenGL,
+                            Target::Spv);
+}
+
 // GLSL-level Vulkan semantics test that need to see the AST for validation.
 TEST_P(VulkanAstSemantics, FromFile)
 {
@@ -206,10 +216,9 @@ INSTANTIATE_TEST_CASE_P(
 INSTANTIATE_TEST_CASE_P(
     Glsl, CompileOpenGLToSpirvTest,
     ::testing::ValuesIn(std::vector<std::string>({
-        // Test looping constructs.
-        // No tests yet for making sure break and continue from a nested loop
-        // goes to the innermost target.
         "spv.atomic.comp",
+        "spv.glFragColor.frag",
+        "spv.specConst.vert",
     })),
     FileNameAsCustomTestSuffix
 );
@@ -224,6 +233,18 @@ INSTANTIATE_TEST_CASE_P(
     FileNameAsCustomTestSuffix
 );
 
+INSTANTIATE_TEST_CASE_P(
+    Glsl, OpenGLSemantics,
+    ::testing::ValuesIn(std::vector<std::string>({
+        "glspv.esversion.vert",
+        "glspv.version.frag",
+        "glspv.version.vert",
+        "glspv.frag",
+        "glspv.vert",
+    })),
+    FileNameAsCustomTestSuffix
+);
+
 INSTANTIATE_TEST_CASE_P(
     Glsl, VulkanAstSemantics,
     ::testing::ValuesIn(std::vector<std::string>({