Plugin Power Saver: Mute throttled plugins.

content/renderer/pepper/plugin_instance_throttler_impl.cc

 // 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 "content/renderer/pepper/plugin_instance_throttler_impl.h"
 
 #include "base/metrics/histogram.h"
 #include "base/time/time.h"
 #include "content/public/common/content_constants.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/renderer/render_frame_impl.h"
 #include "third_party/WebKit/public/platform/WebRect.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "third_party/WebKit/public/web/WebPluginParams.h"
 #include "ui/gfx/color_utils.h"
 #include "url/gurl.h"
 
 namespace content {
 
 namespace {
 
 // Threshold for 'boring' score to accept a frame as good enough to be a
 // representative keyframe. Units are the ratio of all pixels that are within
 // the most common luma bin. The same threshold is used for history thumbnails.
 const double kAcceptableFrameMaximumBoringness = 0.94;
 
 const int kMinimumConsecutiveInterestingFrames = 4;
 
+// When plugin audio is throttled, the plugin will sometimes stop generating
+// video frames. We use this timeout to prevent waiting forever for a good
+// poster image. Chosen arbitrarily.
+const int kAudioThrottledFrameTimeoutMilliseconds = 500;
+
 }  // namespace
 
 // static
 const int PluginInstanceThrottlerImpl::kMaximumFramesToExamine = 150;
 
 // static
 scoped_ptr<PluginInstanceThrottler> PluginInstanceThrottler::Create(
     bool power_saver_enabled) {
   return make_scoped_ptr(new PluginInstanceThrottlerImpl(power_saver_enabled));
 }
 
 // static
 void PluginInstanceThrottler::RecordUnthrottleMethodMetric(
     PluginInstanceThrottlerImpl::PowerSaverUnthrottleMethod method) {
   UMA_HISTOGRAM_ENUMERATION(
       "Plugin.PowerSaver.Unthrottle", method,
       PluginInstanceThrottler::UNTHROTTLE_METHOD_NUM_ITEMS);
 }
 
 PluginInstanceThrottlerImpl::PluginInstanceThrottlerImpl(
     bool power_saver_enabled)
     : state_(power_saver_enabled ? THROTTLER_STATE_AWAITING_KEYFRAME
                                  : THROTTLER_STATE_POWER_SAVER_DISABLED),
       is_hidden_for_placeholder_(false),
       web_plugin_(nullptr),
       consecutive_interesting_frames_(0),
       frames_examined_(0),
+      audio_throttled_(false),
+      audio_throttled_frame_timeout_(
+          FROM_HERE,
+          base::TimeDelta::FromMilliseconds(
+              kAudioThrottledFrameTimeoutMilliseconds),
+          this,
+          &PluginInstanceThrottlerImpl::EngageThrottle),
       weak_factory_(this) {
 }
 
 PluginInstanceThrottlerImpl::~PluginInstanceThrottlerImpl() {
   FOR_EACH_OBSERVER(Observer, observer_list_, OnThrottlerDestroyed());
   if (state_ != THROTTLER_STATE_MARKED_ESSENTIAL)
     RecordUnthrottleMethodMetric(UNTHROTTLE_METHOD_NEVER);
 }
 
 void PluginInstanceThrottlerImpl::AddObserver(Observer* observer) {
@@ skipping 28 matching lines @@
 void PluginInstanceThrottlerImpl::SetHiddenForPlaceholder(bool hidden) {
   is_hidden_for_placeholder_ = hidden;
   FOR_EACH_OBSERVER(Observer, observer_list_, OnHiddenForPlaceholder(hidden));
 }
 
 blink::WebPlugin* PluginInstanceThrottlerImpl::GetWebPlugin() const {
   DCHECK(web_plugin_);
   return web_plugin_;
 }
 
+void PluginInstanceThrottlerImpl::NotifyAudioThrottled() {
+  audio_throttled_ = true;
+  audio_throttled_frame_timeout_.Reset();
+}
+
 void PluginInstanceThrottlerImpl::SetWebPlugin(blink::WebPlugin* web_plugin) {
   DCHECK(!web_plugin_);
   web_plugin_ = web_plugin;
 }
 
 void PluginInstanceThrottlerImpl::Initialize(
     RenderFrameImpl* frame,
     const GURL& content_origin,
     const std::string& plugin_module_name,
     const blink::WebRect& bounds) {
@@ skipping 27 matching lines @@
     return;
 
   ++frames_examined_;
 
   double boring_score = color_utils::CalculateBoringScore(*bitmap);
   if (boring_score <= kAcceptableFrameMaximumBoringness)
     ++consecutive_interesting_frames_;
   else
     consecutive_interesting_frames_ = 0;
 
+  // Does not make a copy, just takes a reference to the underlying pixel data.
+  last_received_frame_ = *bitmap;
+
+  if (audio_throttled_)
+    audio_throttled_frame_timeout_.Reset();
+
   if (frames_examined_ >= kMaximumFramesToExamine ||
       consecutive_interesting_frames_ >= kMinimumConsecutiveInterestingFrames) {
-    FOR_EACH_OBSERVER(Observer, observer_list_, OnKeyframeExtracted(bitmap));
     EngageThrottle();
   }
 }
 
 bool PluginInstanceThrottlerImpl::ConsumeInputEvent(
     const blink::WebInputEvent& event) {
   // Always allow right-clicks through so users may verify it's a plugin.
   // TODO(tommycli): We should instead show a custom context menu (probably
   // using PluginPlaceholder) so users aren't confused and try to click the
   // Flash-internal 'Play' menu item. This is a stopgap solution.
   if (event.modifiers & blink::WebInputEvent::Modifiers::RightButtonDown)
     return false;
 
   if (state_ != THROTTLER_STATE_MARKED_ESSENTIAL &&
       event.type == blink::WebInputEvent::MouseUp &&
       (event.modifiers & blink::WebInputEvent::LeftButtonDown)) {
     bool was_throttled = IsThrottled();
     MarkPluginEssential(UNTHROTTLE_METHOD_BY_CLICK);
     return was_throttled;
   }
 
   return IsThrottled();
 }
 
 void PluginInstanceThrottlerImpl::EngageThrottle() {
   if (state_ != THROTTLER_STATE_AWAITING_KEYFRAME)
     return;
 
+  if (!last_received_frame_.empty()) {
+    FOR_EACH_OBSERVER(Observer, observer_list_,
+                      OnKeyframeExtracted(&last_received_frame_));
+
+    // Release our reference to the underlying pixel data.
+    last_received_frame_.reset();
+  }
+
   state_ = THROTTLER_STATE_PLUGIN_THROTTLED;
   FOR_EACH_OBSERVER(Observer, observer_list_, OnThrottleStateChange());
 }
 
 }  // namespace content