[WebGL 2] primitive restart should be always enabled

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

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index cbb3969024597af40356116aef19adb2d46f2296..c40c02c1a9b9fc8d0baf1bc33e391aa53a036ffd 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -996,6 +996,12 @@ void WebGLRenderingContextBase::initializeNewContext()
     webContext()->setContextLostCallback(m_contextLostCallbackAdapter.get());
     webContext()->setErrorMessageCallback(m_errorMessageCallbackAdapter.get());
 
+    // If WebGL 2, the PRIMITIVE_RESTART_FIXED_INDEX should be always enabled.
+    // See the section <Primitive Restart is Always Enabled> in WebGL 2 spec:
+    // https://www.khronos.org/registry/webgl/specs/latest/2.0/#4.1.4
+    if (isWebGL2OrHigher())
+        contextGL()->Enable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
+
     // This ensures that the context has a valid "lastFlushID" and won't be mistakenly identified as the "least recently used" context.
     contextGL()->Flush();