Don't do a style recalc when updating the composited layer of a plugin.

Source/web/WebPluginContainerImpl.cpp

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 47 matching lines @@
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLPlugInElement.h"
 #include "core/loader/FormState.h"
 #include "core/loader/FrameLoadRequest.h"
 #include "core/page/FocusController.h"
 #include "core/page/Page.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "core/plugins/PluginOcclusionSupport.h"
 #include "core/rendering/HitTestResult.h"
 #include "core/rendering/RenderBox.h"
+#include "core/rendering/RenderLayer.h"
 #include "platform/HostWindow.h"
 #include "platform/KeyboardCodes.h"
 #include "platform/PlatformGestureEvent.h"
 #include "platform/UserGestureIndicator.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/scroll/ScrollAnimator.h"
 #include "platform/scroll/ScrollView.h"
 #include "platform/scroll/ScrollbarTheme.h"
 #include "public/platform/Platform.h"
@@ skipping 203 matching lines @@
     if (!frame)
         return 1.0;
     return frame->pageZoomFactor();
 }
 
 void WebPluginContainerImpl::setWebLayer(WebLayer* layer)
 {
     if (m_webLayer == layer)
         return;
 
-    // If anyone of the layers is null we need to switch between hardware
-    // and software compositing.
-    if (!m_webLayer || !layer) {
-        m_element->setNeedsCompositingUpdate();
-        // Trigger a style recalc so we update the
-        // requiresAcceleratedCompositingForExternalReasons bit in
-        // RenderStyle and thus give the plugin a NormalLayer RenderLayer.
-        m_element->setNeedsStyleRecalc(LocalStyleChange);
-    }
     if (m_webLayer)
         GraphicsLayer::unregisterContentsLayer(m_webLayer);
     if (layer)
         GraphicsLayer::registerContentsLayer(layer);
+
+    // If anyone of the layers is null we need to switch between hardware

[esprehn, 2014/06/10 21:14:37]

"any one" or "either"

+    // and software compositing.
+    bool needsCompositingUpdate = !m_webLayer || !layer;
+
     m_webLayer = layer;
+
+    if (!needsCompositingUpdate)
+        return;
+
+    m_element->setNeedsCompositingUpdate();
+    // Being composited or not affects the self painting layer bit
+    // on the RenderLayer.
+    if (RenderPart* renderer = m_element->renderPart()) {
+        ASSERT(renderer->hasLayer());
+        renderer->layer()->updateSelfPaintingLayer();
+    }
 }
 
 bool WebPluginContainerImpl::supportsPaginatedPrint() const
 {
     return m_webPlugin->supportsPaginatedPrint();
 }
 
 bool WebPluginContainerImpl::isPrintScalingDisabled() const
 {
     return m_webPlugin->isPrintScalingDisabled();
@@ skipping 585 matching lines @@
 
     return clipRect;
 }
 
 bool WebPluginContainerImpl::pluginShouldPersist() const
 {
     return m_webPlugin->shouldPersist();
 }
 
 } // namespace blink