ParallelCompile: Add entry points.

Add the extension text, entry points and validations.

BUG=chromium:849576
TEST=angle_end2end_tests

Change-Id: I4c06ee30e4f4fe9bb1c1fecada747b9c78fed0ea
Reviewed-on: https://chromium-review.googlesource.com/1103789
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jie A Chen <jie.a.chen@intel.com>
diff --git a/src/libANGLE/validationES2.cpp b/src/libANGLE/validationES2.cpp
index f6ff4b3..1a4af01 100644
--- a/src/libANGLE/validationES2.cpp
+++ b/src/libANGLE/validationES2.cpp
@@ -6638,4 +6638,14 @@
                                              depth);
 }
 
+bool ValidateMaxShaderCompilerThreadsKHR(Context *context, GLuint count)
+{
+    if (!context->getExtensions().parallelShaderCompile)
+    {
+        ANGLE_VALIDATION_ERR(context, InvalidOperation(), ExtensionNotEnabled);
+        return false;
+    }
+    return true;
+}
+
 }  // namespace gl