Re-add scrolling of the root frame for plugin windowRects.

third_party/WebKit/Source/web/WebPluginContainerImpl.cpp

Index: third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp b/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
index 64ee6a63899d6412e41b9b5584ab37e14c270921..03872f2667a22c6f76e8d07f150e6b6140b046ae 100644
--- a/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
+++ b/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
@@ -951,9 +951,12 @@ void WebPluginContainerImpl::computeClipRectsForPlugin(
     LayoutRect unclippedAbsoluteRect(frameRectInOwnerElementSpace);
     box->mapRectToPaintInvalidationBacking(rootView, unclippedAbsoluteRect, nullptr);
 
-    // The frameRect is already in absolute space, except for scrolling of the root frame.
+    // The frameRect is already in absolute space of the local frame to the plugin.
     windowRect = frameRect();
+    // Map up to the root frame.
     windowRect = enclosingIntRect(m_element->document().view()->layoutView()->localToAbsoluteQuad(FloatQuad(FloatRect(frameRect())), TraverseDocumentBoundaries).boundingBox());
+    // Finally, adjust for scrolling of the root frame, which the above does not take into account.
+    windowRect.moveBy(roundedIntPoint(-rootView->viewRect().location()));
 
     clippedLocalRect = enclosingIntRect(unclippedAbsoluteRect);
     unclippedIntLocalRect = clippedLocalRect;