WebGL validation for depthRange.

Generate INVALID_OPERATION for depthRange(zNear, zFar) if zNear > zFar.
Add corresponding test.

BUG=angleproject:1816

Change-Id: I28b5876a74c9765c0eef1e0f6e5e96d0380586d0
Reviewed-on: https://chromium-review.googlesource.com/441207
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/validationES2.cpp b/src/libANGLE/validationES2.cpp
index 43a1b47..ddc1a2e 100644
--- a/src/libANGLE/validationES2.cpp
+++ b/src/libANGLE/validationES2.cpp
@@ -4015,4 +4015,15 @@
     return true;
 }
 
+bool ValidateDepthRangef(ValidationContext *context, GLclampf zNear, GLclampf zFar)
+{
+    if (context->getExtensions().webglCompatibility && zNear > zFar)
+    {
+        context->handleError(Error(GL_INVALID_OPERATION, "Depth near > far."));
+        return false;
+    }
+
+    return true;
+}
+
 }  // namespace gl