Media Controls: invalidate volume slider when value changes.

third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 838 matching lines @@
 }
 
 bool MediaControlVolumeSliderElement::willRespondToMouseClickEvents() {
   if (!isConnected() || !document().isActive())
     return false;
 
   return MediaControlInputElement::willRespondToMouseClickEvents();
 }
 
 void MediaControlVolumeSliderElement::setVolume(double volume) {
-  if (value().toDouble() != volume)
-    setValue(String::number(volume));
+  if (value().toDouble() == volume)

[whywhat, 2017/01/09 16:06:59]

nit: is it okay to compare doubles like this? I remember that doing something
like abs(a - b) < epsilon is better in general - do we have a method for that in
WTF or base and does it matter? (e.g. if the volume values are always within 0-1
range with 0.1 intervals, it shouldn't)

[mlamouri (slow - plz ping), 2017/01/10 14:13:19]

In general, we can assume that any change is meaningful. There might be an
epsilon we could use but we could easily end up with issues such as many epsilon
changes leading to a large change we have been ignoring.

+    return;
+
+  setValue(String::number(volume));
+  if (LayoutObject* layoutObject = this->layoutObject())
+    layoutObject->setShouldDoFullPaintInvalidation();
 }
 
 bool MediaControlVolumeSliderElement::keepEventInNode(Event* event) {
   return isUserInteractionEventForSlider(event, layoutObject());
 }
 
 // ----------------------------
 
 MediaControlFullscreenButtonElement::MediaControlFullscreenButtonElement(
     MediaControls& mediaControls)
@@ skipping 170 matching lines @@
 MediaControlCurrentTimeDisplayElement*
 MediaControlCurrentTimeDisplayElement::create(MediaControls& mediaControls) {
   MediaControlCurrentTimeDisplayElement* element =
       new MediaControlCurrentTimeDisplayElement(mediaControls);
   element->setShadowPseudoId(
       AtomicString("-webkit-media-controls-current-time-display"));
   return element;
 }
 
 }  // namespace blink