LibWeb: Fix WebGL getError

getError was just calling out to glGetError and never checking our
error value that we were maintaining ourselves.

Libraries/LibWeb/WebGL/WebGLRenderingContextBase.cpp

@@ -195,8 +195,23 @@ Optional<WebGLRenderingContextBase::ConvertedTexture> WebGLRenderingContextBase:
     };
 }
 
+// TODO: The glGetError spec allows for queueing errors which is something we should probably do, for now
+//       this just keeps track of one error which is also fine by the spec
+GLenum WebGLRenderingContextBase::get_error_value()
+{
+    if (m_error == GL_NO_ERROR)
+        return glGetError();
+
+    auto error = m_error;
+    m_error = GL_NO_ERROR;
+    return error;
+}
+
 void WebGLRenderingContextBase::set_error(GLenum error)
 {
+    if (m_error != GL_NO_ERROR)
+        return;
+
     auto context_error = glGetError();
     if (context_error != GL_NO_ERROR)
         m_error = context_error;

Libraries/LibWeb/WebGL/WebGLRenderingContextBase.h

@@ -138,6 +138,7 @@ protected:
         return result;
     }
 
+    GLenum get_error_value();
     void set_error(GLenum error);
 
     // UNPACK_FLIP_Y_WEBGL of type boolean

Libraries/LibWeb/WebGL/WebGLRenderingContextImpl.cpp

@@ -1535,7 +1535,7 @@ JS::Value WebGLRenderingContextImpl::get_parameter(WebIDL::UnsignedLong pname)
 WebIDL::UnsignedLong WebGLRenderingContextImpl::get_error()
 {
     m_context->make_current();
-    return glGetError();
+    return get_error_value();
 }
 
 JS::Value WebGLRenderingContextImpl::get_program_parameter(GC::Root<WebGLProgram> program, WebIDL::UnsignedLong pname)