Make slider thumb painting bail out when the node is null.

Source/core/rendering/RenderMediaControls.cpp

Index: Source/core/rendering/RenderMediaControls.cpp
diff --git a/Source/core/rendering/RenderMediaControls.cpp b/Source/core/rendering/RenderMediaControls.cpp
index 6288aa3969d8087ddf1e4f2898fa61c128ea5b9a..b08ee2e510ee3163c9c7fc9bc86fe6523a72aa0e 100644
--- a/Source/core/rendering/RenderMediaControls.cpp
+++ b/Source/core/rendering/RenderMediaControls.cpp
@@ -246,7 +246,9 @@ static bool paintMediaSlider(RenderObject* object, const PaintInfo& paintInfo, c
 
 static bool paintMediaSliderThumb(RenderObject* object, const PaintInfo& paintInfo, const IntRect& rect)
 {
-    ASSERT(object->node());
+    if (!object->node())
+        return false;
+
     HTMLMediaElement* mediaElement = toParentMediaElement(object->node()->shadowHost());
     if (!mediaElement)
         return false;
@@ -299,7 +301,9 @@ static bool paintMediaVolumeSlider(RenderObject* object, const PaintInfo& paintI
 
 static bool paintMediaVolumeSliderThumb(RenderObject* object, const PaintInfo& paintInfo, const IntRect& rect)
 {
-    ASSERT(object->node());
+    if (!object->node())
+        return false;
+
     HTMLMediaElement* mediaElement = toParentMediaElement(object->node()->shadowHost());
     if (!mediaElement)
         return false;