SpeechRecognizerImpl: use a WeakPtr to itself for all tasks

It seems that during shutdown, SpeechRecognizerImpl can go away before the
posted task runs. This is similar to crrev.com/729694.

(cherry picked from commit 0b2aaaa8a4948d88b892c3e6cabc87848f248e52)

Bug: 1067851
Change-Id: I1c43d3bfaf978891f4abaef8e452a088d0f18c5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2139701
Reviewed-by: Primiano Tucci <primiano@chromium.org>
Reviewed-by: Tommi <tommi@chromium.org>
Reviewed-by: Olga Sharonova <olka@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#757385}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2148952
Reviewed-by: Ben Mason <benmason@chromium.org>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Ben Mason <benmason@chromium.org>
Cr-Commit-Position: refs/branch-heads/4044@{#926}
Cr-Branched-From: a6d9daf149a473ceea37f629c41d4527bf2055bd-refs/heads/master@{#737173}

content/browser/speech/speech_recognizer_impl.cc

diff --git a/content/browser/speech/speech_recognizer_impl.cc b/content/browser/speech/speech_recognizer_impl.cc
index bd64fae..b03a554 100644
--- a/content/browser/speech/speech_recognizer_impl.cc
+++ b/content/browser/speech/speech_recognizer_impl.cc
@@ -224,7 +224,8 @@
   device_id_ = device_id;
 
   base::PostTask(FROM_HERE, {BrowserThread::IO},
-                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this,
+                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                weak_ptr_factory_.GetWeakPtr(),
                                 FSMEventArgs(EVENT_PREPARE)));
 }
 
@@ -237,7 +238,8 @@
 
 void SpeechRecognizerImpl::StopAudioCapture() {
   base::PostTask(FROM_HERE, {BrowserThread::IO},
-                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this,
+                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                weak_ptr_factory_.GetWeakPtr(),
                                 FSMEventArgs(EVENT_STOP_CAPTURE)));
 }
 
@@ -276,16 +278,16 @@
   // Convert audio from native format to fixed format used by WebSpeech.
   FSMEventArgs event_args(EVENT_AUDIO_DATA);
   event_args.audio_data = audio_converter_->Convert(data);
-  base::PostTask(
-      FROM_HERE, {BrowserThread::IO},
-      base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this, event_args));
+  base::PostTask(FROM_HERE, {BrowserThread::IO},
+                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                weak_ptr_factory_.GetWeakPtr(), event_args));
   // See http://crbug.com/506051 regarding why one extra convert call can
   // sometimes be required. It should be a rare case.
   if (!audio_converter_->data_was_converted()) {
     event_args.audio_data = audio_converter_->Convert(data);
-    base::PostTask(
-        FROM_HERE, {BrowserThread::IO},
-        base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this, event_args));
+    base::PostTask(FROM_HERE, {BrowserThread::IO},
+                   base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                  weak_ptr_factory_.GetWeakPtr(), event_args));
   }
   // Something is seriously wrong here and we are most likely missing some
   // audio segments.
@@ -294,18 +296,18 @@
 
 void SpeechRecognizerImpl::OnCaptureError(const std::string& message) {
   FSMEventArgs event_args(EVENT_AUDIO_ERROR);
-  base::PostTask(
-      FROM_HERE, {BrowserThread::IO},
-      base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this, event_args));
+  base::PostTask(FROM_HERE, {BrowserThread::IO},
+                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                weak_ptr_factory_.GetWeakPtr(), event_args));
 }
 
 void SpeechRecognizerImpl::OnSpeechRecognitionEngineResults(
     const std::vector<blink::mojom::SpeechRecognitionResultPtr>& results) {
   FSMEventArgs event_args(EVENT_ENGINE_RESULT);
   event_args.engine_results = mojo::Clone(results);
-  base::PostTask(
-      FROM_HERE, {BrowserThread::IO},
-      base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this, event_args));
+  base::PostTask(FROM_HERE, {BrowserThread::IO},
+                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                weak_ptr_factory_.GetWeakPtr(), event_args));
 }
 
 void SpeechRecognizerImpl::OnSpeechRecognitionEngineEndOfUtterance() {
@@ -317,9 +319,9 @@
     const blink::mojom::SpeechRecognitionError& error) {
   FSMEventArgs event_args(EVENT_ENGINE_ERROR);
   event_args.engine_error = error;
-  base::PostTask(
-      FROM_HERE, {BrowserThread::IO},
-      base::BindOnce(&SpeechRecognizerImpl::DispatchEvent, this, event_args));
+  base::PostTask(FROM_HERE, {BrowserThread::IO},
+                 base::BindOnce(&SpeechRecognizerImpl::DispatchEvent,
+                                weak_ptr_factory_.GetWeakPtr(), event_args));
 }
 
 // -----------------------  Core FSM implementation ---------------------------