Replace AudioSilenceDetector with an AudioPowerMonitor.

chrome/browser/media/audio_stream_indicator.cc

Index: chrome/browser/media/audio_stream_indicator.cc
diff --git a/chrome/browser/media/audio_stream_indicator.cc b/chrome/browser/media/audio_stream_indicator.cc
index 6cd623212e72fcf8dcc722241af868ec291d5755..1d3aa7216486273129a76b8e846852884ee6ad20 100644
--- a/chrome/browser/media/audio_stream_indicator.cc
+++ b/chrome/browser/media/audio_stream_indicator.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/media/audio_stream_indicator.h"
 
+#include <limits>
+
 #include "base/bind.h"
 #include "chrome/browser/tab_contents/tab_util.h"
 #include "content/public/browser/browser_thread.h"
@@ -20,58 +22,106 @@ AudioStreamIndicator::~AudioStreamIndicator() {}
 
 void AudioStreamIndicator::UpdateWebContentsStatus(
     int render_process_id, int render_view_id, int stream_id,
-    bool is_playing_and_audible) {
+    bool is_playing, float power_dbfs, bool clipped) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&AudioStreamIndicator::UpdateWebContentsStatusOnUIThread, this,
                  render_process_id, render_view_id, stream_id,
-                 is_playing_and_audible));
+                 is_playing, power_dbfs, clipped));
 }
 
-bool AudioStreamIndicator::IsPlayingAudio(WebContents* contents) {
+bool AudioStreamIndicator::IsPlayingAudio(const WebContents* contents) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  RenderViewId id(contents->GetRenderProcessHost()->GetID(),
-                  contents->GetRenderViewHost()->GetRoutingID());
-  return audio_streams_.find(id) != audio_streams_.end();
+  // TODO(miu): In order to prevent breaking existing uses of this method, the
+  // old semantics of "playing AND not silent" have been retained here.  Once
+  // the tab audio indicator UI switches over to using the new
+  // GetAudioSignalPower(), this method should really be just "playing."
+  float level;
+  bool ignored;
+  CurrentAudibleLevel(contents, &level, &ignored);
+  return level > 0.0f;
 }
 
-AudioStreamIndicator::RenderViewId::RenderViewId(int render_process_id,
-                                                 int render_view_id)
-    : render_process_id(render_process_id),
-      render_view_id(render_view_id) {
-}
+void AudioStreamIndicator::CurrentAudibleLevel(
+    const content::WebContents* contents, float* level, bool* clipped) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  float max_power_dbfs = -std::numeric_limits<float>::infinity();
+  bool has_clipped = false;
 
-bool AudioStreamIndicator::RenderViewId::operator<(
-    const RenderViewId& other) const {
-  if (render_process_id != other.render_process_id)
-    return render_process_id < other.render_process_id;
+  // Since a RenderView can have more than one stream playing back, return the
+  // maximum of the last-reported power levels.  For more information about how
+  // the power level is measured, see media/audio/audio_power_monitor.h.
+  const RenderViewId id(contents->GetRenderProcessHost()->GetID(),
+                        contents->GetRenderViewHost()->GetRoutingID());
+  RenderViewStreamMap::const_iterator view_it = audio_streams_.find(id);
+  if (view_it != audio_streams_.end()) {
+    const StreamPowerLevels& stream_levels = view_it->second;
+    for (StreamPowerLevels::const_iterator stream_it = stream_levels.begin();
+         stream_it != stream_levels.end(); ++stream_it) {
+      if (stream_it->power_dbfs > max_power_dbfs)
+        max_power_dbfs = stream_it->power_dbfs;
+      has_clipped |= stream_it->clipped;
+    }
+  }
 
-  return render_view_id < other.render_view_id;
+  // Map the power into an "audible level" in the range [0.0,1.0].  dBFS values
+  // are in the range -inf (minimum power) to 0.0 (maximum power).
+  static const float kSilenceThresholdDBFS = -72.24719896f;
+  if (max_power_dbfs < kSilenceThresholdDBFS)
+    *level = 0.0f;
+  else if (max_power_dbfs > 0.0f)
+    *level = 1.0f;
+  else
+    *level = 1.0f - max_power_dbfs / kSilenceThresholdDBFS;
+  *clipped = has_clipped;
 }
 
 void AudioStreamIndicator::UpdateWebContentsStatusOnUIThread(
-    int render_process_id,
-    int render_view_id,
-    int stream_id,
-    bool is_playing_and_audible) {
+    int render_process_id, int render_view_id, int stream_id,
+    bool is_playing, float power_dbfs, bool clipped) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  RenderViewId id(render_process_id, render_view_id);
-  if (is_playing_and_audible) {
-    audio_streams_[id].insert(stream_id);
+
+  const RenderViewId id(render_process_id, render_view_id);
+  if (is_playing) {
+    // Find the StreamPowerLevel instance associated with |stream_id|, or
+    // auto-create a new one.
+    StreamPowerLevels& stream_levels = audio_streams_[id];
+    StreamPowerLevels::iterator stream_it;
+    for (stream_it = stream_levels.begin(); stream_it != stream_levels.end();
+         ++stream_it) {
+      if (stream_it->stream_id == stream_id)
+        break;
+    }
+    if (stream_it == stream_levels.end()) {
+      stream_it = stream_levels.insert(stream_levels.end(), StreamPowerLevel());
+      stream_it->stream_id = stream_id;
+    }
+
+    // Update power and clip values.
+    stream_it->power_dbfs = power_dbfs;
+    stream_it->clipped = clipped;
   } else {
-    std::map<RenderViewId, std::set<int> >::iterator it =
-        audio_streams_.find(id);
-    if (it == audio_streams_.end())
-      return;
-
-    it->second.erase(stream_id);
-    if (it->second.empty())
-      audio_streams_.erase(it);
+    // Find and erase the StreamPowerLevel instance associated with |stream_id|.
+    RenderViewStreamMap::iterator view_it = audio_streams_.find(id);
+    if (view_it != audio_streams_.end()) {
+      StreamPowerLevels& stream_levels = view_it->second;
+      for (StreamPowerLevels::iterator stream_it = stream_levels.begin();
+           stream_it != stream_levels.end(); ++stream_it) {
+        if (stream_it->stream_id == stream_id) {
+          stream_levels.erase(stream_it);
+          if (stream_levels.empty())
+            audio_streams_.erase(view_it);
+          break;
+        }
+      }
+    }
   }
 
+  // Trigger UI update.
   WebContents* web_contents = tab_util::GetWebContentsByID(render_process_id,
                                                            render_view_id);
   if (web_contents)