Add speech recognition context to the Web Speech API

Explainer for speech recognition context is added in #140

Author: yrw-google

.gitignore

@@ -1 +1,3 @@
 index.html
+.DS_Store
+.idea/

index.bs

@@ -161,12 +161,14 @@ interface SpeechRecognition : EventTarget {
     attribute boolean interimResults;
     attribute unsigned long maxAlternatives;
     attribute SpeechRecognitionMode mode;
+    attribute SpeechRecognitionContext context;
 
     // methods to drive the speech interaction
     undefined start();
     undefined start(MediaStreamTrack audioTrack);
     undefined stop();
     undefined abort();
+    undefined updateContext(SpeechRecognitionContext context);
     static Promise<boolean> availableOnDevice(DOMString lang);
     static Promise<boolean> installOnDevice(DOMString lang);
 
@@ -191,7 +193,8 @@ enum SpeechRecognitionErrorCode {
     "network",
     "not-allowed",
     "service-not-allowed",
-    "language-not-supported"
+    "language-not-supported",
+    "recognition-context-not-supported"
 };
 
 enum SpeechRecognitionMode {
@@ -246,6 +249,28 @@ dictionary SpeechRecognitionEventInit : EventInit {
     unsigned long resultIndex = 0;
     required SpeechRecognitionResultList results;
 };
+
+// The object representing a biasing phrase.
+[Exposed=Window]
+interface SpeechRecognitionPhrase {
+    // If the phrase is empty or the boost is outside the range [0, 10], throw a "SyntaxError" DOMException.
+    constructor(DOMString phrase, optional float boost = 1.0);
+    attribute DOMString phrase;
+    attribute float boost;
+};
+
+// The object representing a list of biasing phrases.
+[Exposed=Window]
+interface SpeechRecognitionPhraseList {
+    readonly attribute unsigned long length;
+    getter SpeechRecognitionPhrase item(unsigned long index);
+};
+
+// The object representing a recognition context collection.
+[Exposed=Window]
+interface SpeechRecognitionContext {
+    attribute SpeechRecognitionPhraseList phrases;
+};
 </xmp>
 
 <h4 id="speechreco-attributes">SpeechRecognition Attributes</h4>
@@ -276,6 +301,10 @@ dictionary SpeechRecognitionEventInit : EventInit {
 
   <dt><dfn attribute for=SpeechRecognition>mode</dfn> attribute</dt>
   <dd>An enum to determine where speech recognition takes place. The default value is "ondevice-preferred".</dd>
+
+  <dt><dfn attribute for=SpeechRecognition>context</dfn> attribute</dt>
+  <dd>This attribute will set the speech recognition context for the recognition session to start with.
+  If the speech recognition model does not support recognition context, a {{SpeechRecognitionErrorEvent}} with the {{recognition-context-not-supported}} error code will be thrown.</dd>
 </dl>
 
 <p class=issue>The group has discussed whether WebRTC might be used to specify selection of audio sources and remote recognizers.
@@ -319,6 +348,9 @@ See <a href="https://lists.w3.org/Archives/Public/public-speech-api/2012Sep/0072
   <dt><dfn method for=SpeechRecognition>installOnDevice({{DOMString}} lang)</dfn> method</dt>
   <dd>The installOnDevice method returns a Promise that resolves to a boolean indicating whether the installation of on-device speech recognition for a given BCP 47 language tag initiated successfully. [[!BCP47]]</dd>
 
+  <dt><dfn method for=SpeechRecognition>updateContext({{SpeechRecognitionContext}} context)</dfn> method</dt>
+  <dd>The updateContext method updates the speech recognition context after the speech recognition session has started. If the recognition session is not active when this method is called, throw an {{InvalidStateError}} and abort.
+  If the speech recognition model does not support recognition context, throw a {{SpeechRecognitionErrorEvent}} with the {{recognition-context-not-supported}} error code and abort.</dd>
 </dl>
 
 <p>When the <dfn>start session algorithm</dfn> with <var>requestMicrophonePermission</var> is invoked, the user agent MUST run the following steps:
@@ -421,6 +453,9 @@ For example, some implementations may fire <a event for=SpeechRecognition>audioe
 
     <dt><dfn enum-value for=SpeechRecognitionErrorCode>"language-not-supported"</dfn></dt>
     <dd>The language was not supported.</dd>
+
+    <dt><dfn enum-value for=SpeechRecognitionErrorCode>"recognition-context-not-supported"</dfn></dt>
+    <dd>The speech recognition model does not support recognition context.</dd>
   </dl>
   </dd>