Plugin Power Saver: Add UI Overlay to throttled plugin using placeholder.

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_frame.h"
@@ skipping 42 matching lines @@
       PluginInstanceThrottler::UNTHROTTLE_METHOD_NUM_ITEMS);
 }
 
 PluginInstanceThrottlerImpl::PluginInstanceThrottlerImpl(
     RenderFrame* frame,
     const GURL& plugin_url,
     bool power_saver_enabled)
     : state_(power_saver_enabled ? POWER_SAVER_ENABLED_AWAITING_KEYFRAME
                                  : POWER_SAVER_DISABLED),
       consecutive_interesting_frames_(0),
+      keyframe_extraction_timed_out_(false),
       weak_factory_(this) {
   // To collect UMAs, register peripheral content even if power saver disabled.
   if (frame) {
     frame->RegisterPeripheralPlugin(
         plugin_url.GetOrigin(),
         base::Bind(&PluginInstanceThrottlerImpl::MarkPluginEssential,
                    weak_factory_.GetWeakPtr(), UNTHROTTLE_METHOD_BY_WHITELIST));
   }
 
   if (power_saver_enabled) {
     base::MessageLoop::current()->PostDelayedTask(
-        FROM_HERE, base::Bind(&PluginInstanceThrottlerImpl::EngageThrottle,
-                              weak_factory_.GetWeakPtr()),
+        FROM_HERE,
+        base::Bind(&PluginInstanceThrottlerImpl::TimeoutKeyframeExtraction,
+                   weak_factory_.GetWeakPtr()),
         base::TimeDelta::FromMilliseconds(kThrottleTimeout));
   }
 }
 
 PluginInstanceThrottlerImpl::~PluginInstanceThrottlerImpl() {
+  FOR_EACH_OBSERVER(Observer, observer_list_, OnThrottlerDestroyed());
   if (state_ != PLUGIN_INSTANCE_MARKED_ESSENTIAL)
     RecordUnthrottleMethodMetric(UNTHROTTLE_METHOD_NEVER);
 }
 
 void PluginInstanceThrottlerImpl::AddObserver(Observer* observer) {
   observer_list_.AddObserver(observer);
 }
 
 void PluginInstanceThrottlerImpl::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
@@ skipping 20 matching lines @@
   DCHECK(needs_representative_keyframe());
   if (!bitmap)
     return;
 
   double boring_score = color_utils::CalculateBoringScore(*bitmap);
   if (boring_score <= kAcceptableFrameMaximumBoringness)
     ++consecutive_interesting_frames_;
   else
     consecutive_interesting_frames_ = 0;
 
-  if (consecutive_interesting_frames_ >= kMinimumConsecutiveInterestingFrames)
+  if (keyframe_extraction_timed_out_ ||
+      consecutive_interesting_frames_ >= kMinimumConsecutiveInterestingFrames) {
+    FOR_EACH_OBSERVER(Observer, observer_list_, OnKeyframeExtracted(bitmap));

[groby-ooo-7-16, 2015/01/30 02:22:44]

Do we expect multiple observers? 

[tommycli, 2015/01/30 17:02:40]

In general, yes. For this particular call, there's currently only one observer.
The other observers have noop stub methods.

     EngageThrottle();
+  }
 }
 
 bool PluginInstanceThrottlerImpl::ConsumeInputEvent(
     const blink::WebInputEvent& event) {
   // Always allow right-clicks through so users may verify it's a plug-in.
   // 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;
@@ skipping 10 matching lines @@
 }
 
 void PluginInstanceThrottlerImpl::EngageThrottle() {
   if (state_ != POWER_SAVER_ENABLED_AWAITING_KEYFRAME)
     return;
 
   state_ = POWER_SAVER_ENABLED_PLUGIN_THROTTLED;
   FOR_EACH_OBSERVER(Observer, observer_list_, OnThrottleStateChange());
 }
 
+void PluginInstanceThrottlerImpl::TimeoutKeyframeExtraction() {
+  DCHECK(!keyframe_extraction_timed_out_);

[groby-ooo-7-16, 2015/01/30 02:22:44]

Why do we care about this as a precondition? Will anything go wrong if this is
called twice?

[tommycli, 2015/01/30 17:02:40]

Done.

+  keyframe_extraction_timed_out_ = true;
+}
+
 }  // namespace content