Fix transform feedback bugs

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index de0568a5dc1e9c93b40a66087efe5ba3414aa34b..84b498098526d81694197bbdbd9669fad5d96679 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -2006,6 +2006,10 @@ WebGLTransformFeedback* WebGL2RenderingContextBase::createTransformFeedback()
 
 void WebGL2RenderingContextBase::deleteTransformFeedback(WebGLTransformFeedback* feedback)
 {
+    if (transformFeedbackActive()) {
+        synthesizeGLError(GL_INVALID_OPERATION, "deleteTransformFeedback", "transform feedback is active");
+        return;
+    }
     if (feedback == m_transformFeedbackBinding)
         m_transformFeedbackBinding = nullptr;