The effect of the grammar in the Web Speech API

Question

In examples for the Web Speech API, a grammar is always specified. For example, in MDN's colour change example, the grammar is:

#JSGF V1.0;
grammar colors;
public <color> = aqua | azure | beige | bisque | black | blue | brown | chocolate | coral | crimson | cyan | fuchsia | ghostwhite | gold | goldenrod | gray | green | indigo | ivory | khaki | lavender | lime | linen | magenta | maroon | moccasin | navy | olive | orange | orchid | peru | pink | plum | purple | red | salmon | sienna | silver | snow | tan | teal | thistle | tomato | turquoise | violet | white | yellow ;

However, in actually using the API (on Chrome 54.0.2840.71), the result function:

1. Sometimes returns strings that do not fit the supplied grammar
2. Does not provide the parse tree that describes the speech

What then does the grammar actually do? How can I get either of these behaviours (restricting to the grammar and seeing the parse tree)?

Answer 1

There's currently an open Chromium issue specifically about this:

https://bugs.chromium.org/p/chromium/issues/detail?id=799849&q=SpeechRecognition%20grammar&colspec=ID%20Pri%20M%20Stars%20ReleaseBlock%20Component%20Status%20Owner%20Summary%20OS%20Modified