The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1099273f5452a87dbb35502d120bf84a5acbe0dc

commit 1099273f5452a87dbb35502d120bf84a5acbe0dc
Author: Dominic Mazzoni <dmazzoni@chromium.org>
Date: Tue Oct 23 04:27:16 2018

Store TTS engine extension voices in extension prefs.

A TTS engine extension can advertise the set of voices it provides
either using the extension manifest, or by calling
chrome.ttsEngine.updateVoices to provide a dynamic list.

Previously we cached the set of dynamic voices provided by updateVoices
in a map in TtsEngineExtensionObserver. That works fine if a TTS extension
has a chance to run.

However, on profile load, installed extensions don't typically run. That means
that when a web page queries the set of installed voices, it gets the
list of voices from the manifest, not the dynamic list of voices. This is
only fixed once the extension spins up, typically when speech starts.

Instead, when an extension calls chrome.ttsEngine.updateVoices, cache
the voices in the extension preferences, so that when a profile loads it
always gets the most up-to-date list of voices.

Partially covered by the existing TtsApiTest.UpdateVoicesApi test,
and adds a new 2-part test to cover the caching in particular.

(This supercedes: http://crrev.com/c/1247023)

Bug:  889591 
Change-Id: I79d8e576114951869af66e682920672924f247a7
Reviewed-on: https://chromium-review.googlesource.com/c/1263035
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601848}
[modify] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
[modify] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/browser/speech/extension_api/tts_engine_extension_observer.cc
[modify] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/browser/speech/extension_api/tts_engine_extension_observer.h
[modify] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/browser/speech/extension_api/tts_extension_apitest.cc
[add] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/test/data/extensions/api_test/tts_engine/call_update_voices/manifest.json
[add] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/test/data/extensions/api_test/tts_engine/call_update_voices/test.js
[modify] https://crrev.com/1099273f5452a87dbb35502d120bf84a5acbe0dc/chrome/test/data/extensions/api_test/tts_engine/update_voices_api/test.js