Removes sub-entry-point Framebuffer validations

BUG=angle:685

Change-Id: I2d630396a5971972f858cca9c39ceb6509492aa4
Reviewed-on: https://chromium-review.googlesource.com/205836
Tested-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libGLESv2/validationES.cpp b/src/libGLESv2/validationES.cpp
index 6ee4cae..a9e04e5 100644
--- a/src/libGLESv2/validationES.cpp
+++ b/src/libGLESv2/validationES.cpp
@@ -360,6 +360,11 @@
 bool ValidateFramebufferRenderbufferParameters(gl::Context *context, GLenum target, GLenum attachment,
                                                GLenum renderbuffertarget, GLuint renderbuffer)
 {
+    if (!ValidFramebufferTarget(target))
+    {
+        return gl::error(GL_INVALID_ENUM, false);
+    }
+
     gl::Framebuffer *framebuffer = context->getTargetFramebuffer(target);
     GLuint framebufferHandle = context->getTargetFramebufferHandle(target);