[AW] Web Speech API: enable speech recognition in WebView.

Enable the Speech recognition part of the Web Speech API in
Android WebView. Speech synthesis API remains disabled for
now, see crbug.com/487255.

BUG=487255
TEST=https://www.google.com/intl/en/chrome/demos/speech.html

Change-Id: Id2c2654c34f63a5ba2ac883614a24b18ab419015
Reviewed-on: https://chromium-review.googlesource.com/c/1340318
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610104}

android_webview/lib/aw_main_delegate.cc

@@ -101,8 +101,9 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
   // WebView does not yet support screen orientation locking.
   cl->AppendSwitch(switches::kDisableScreenOrientationLock);
 
-  // WebView does not currently support Web Speech API (crbug.com/487255)
-  cl->AppendSwitch(switches::kDisableSpeechAPI);
+  // WebView does not currently support Web Speech Synthesis API,
+  // but it does support Web Speech Recognition API (crbug.com/487255).
+  cl->AppendSwitch(switches::kDisableSpeechSynthesisAPI);
 
   // WebView does not currently support the Permissions API (crbug.com/490120)
   cl->AppendSwitch(switches::kDisablePermissionsAPI);

android_webview/tools/system_webview_shell/test/data/webexposed/not-webview-exposed.txt

-# speech api not enabled in webview, crbug.com/487255
+# speech synthesis api not enabled in webview
+# but speech recognition is enabled, crbug.com/487255
 interface SpeechSynthesisErrorEvent : SpeechSynthesisEvent
 interface SpeechSynthesisEvent : Event
 interface SpeechSynthesisUtterance : EventTarget
-interface webkitSpeechGrammar
-interface webkitSpeechGrammarList
-interface webkitSpeechRecognition : EventTarget
-interface webkitSpeechRecognitionError : Event
-interface webkitSpeechRecognitionEvent : Event
 
 # permissions api not enabled in webview, crbug.com/490120
 interface PermissionStatus : EventTarget