Replumb audible playback detection to use a poll-based approach.

The previous approach involved hopping across three threads for every data update, and was riddled with a number of other warts.  This change contains a rewrite of AudioStreamIndicator (now called AudioStreamMonitor) to: 1) use an efficient polling-based approach for audible tab detection; 2) resolve bug 339133 by using simple debouncing logic; 3) solve the problem of massively redundantly notifying the tab UI when no state changes occur.  Also, this functionality now has unit tests where it did not before.

Other changes:

1. Adding miu@ to OWNERS for tab media indicator-related code.
2. While making interface changes in MediaObserver, I did a little work to help migrate from render view IDs to render frame IDs.

BUG=339133
TEST=New AudioStreamMonitorTest's in unit_tests.  Also, manually confirmed behavior fixes using repro steps in bug 339133.

Review URL: https://codereview.chromium.org/135013008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256346 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/media/OWNERS

@@ -14,3 +14,7 @@ per-file cast_*=hclam@chromium.org
 per-file cast_*=hubbe@chromium.org
 per-file cast_*=mikhal@chromium.org
 per-file cast_*=pwestin@google.com
+
+# For changes related to the tab media indicators.
+per-file audio_stream_monitor*=miu@chromium.org
+per-file media_stream_capture_indicator*=miu@chromium.org

chrome/browser/media/audio_stream_monitor.cc

@@ -0,0 +1,86 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/media/audio_stream_monitor.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "content/public/browser/invalidate_type.h"
+#include "content/public/browser/web_contents.h"
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(AudioStreamMonitor);
+
+AudioStreamMonitor::AudioStreamMonitor(content::WebContents* contents)
+    : web_contents_(contents),
+      clock_(&default_tick_clock_),
+      was_recently_audible_(false) {
+  DCHECK(web_contents_);
+}
+
+AudioStreamMonitor::~AudioStreamMonitor() {}
+
+bool AudioStreamMonitor::WasRecentlyAudible() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return was_recently_audible_;
+}
+
+void AudioStreamMonitor::StartMonitoringStream(
+    int stream_id,
+    const ReadPowerAndClipCallback& read_power_callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!read_power_callback.is_null());
+  poll_callbacks_[stream_id] = read_power_callback;
+  if (!poll_timer_.IsRunning()) {
+    poll_timer_.Start(
+        FROM_HERE,
+        base::TimeDelta::FromSeconds(1) / kPowerMeasurementsPerSecond,
+        base::Bind(&AudioStreamMonitor::Poll, base::Unretained(this)));
+  }
+}
+
+void AudioStreamMonitor::StopMonitoringStream(int stream_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  poll_callbacks_.erase(stream_id);
+  if (poll_callbacks_.empty())
+    poll_timer_.Stop();
+}
+
+void AudioStreamMonitor::Poll() {
+  for (StreamPollCallbackMap::const_iterator it = poll_callbacks_.begin();
+       it != poll_callbacks_.end();
+       ++it) {
+    // TODO(miu): A new UI for delivering specific power level and clipping
+    // information is still in the works.  For now, we throw away all
+    // information except for "is it audible?"
+    const float power_dbfs = it->second.Run().first;
+    const float kSilenceThresholdDBFS = -72.24719896f;
+    if (power_dbfs >= kSilenceThresholdDBFS) {
+      last_blurt_time_ = clock_->NowTicks();
+      MaybeToggle();
+      break;  // No need to poll remaining streams.
+    }
+  }
+}
+
+void AudioStreamMonitor::MaybeToggle() {
+  const bool indicator_was_on = was_recently_audible_;
+  const base::TimeTicks off_time =
+      last_blurt_time_ + base::TimeDelta::FromMilliseconds(kHoldOnMilliseconds);
+  const base::TimeTicks now = clock_->NowTicks();
+  const bool should_indicator_be_on = now < off_time;
+
+  if (should_indicator_be_on != indicator_was_on) {
+    was_recently_audible_ = should_indicator_be_on;
+    web_contents_->NotifyNavigationStateChanged(content::INVALIDATE_TYPE_TAB);
+  }
+
+  if (!should_indicator_be_on) {
+    off_timer_.Stop();
+  } else if (!off_timer_.IsRunning()) {
+    off_timer_.Start(
+        FROM_HERE,
+        off_time - now,
+        base::Bind(&AudioStreamMonitor::MaybeToggle, base::Unretained(this)));
+  }
+}