Fix fixed-background offset issue

Source/core/paint/BackgroundImageGeometry.cpp

Index: Source/core/paint/BackgroundImageGeometry.cpp
diff --git a/Source/core/paint/BackgroundImageGeometry.cpp b/Source/core/paint/BackgroundImageGeometry.cpp
index d4a3bedff08bf0af15358b19fe13c291f3f5f1f4..a548ce89a4f69e9c528980a447151935ea1d6312 100644
--- a/Source/core/paint/BackgroundImageGeometry.cpp
+++ b/Source/core/paint/BackgroundImageGeometry.cpp
@@ -127,6 +127,20 @@ IntSize calculateFillTileSize(const LayoutBoxModelObject& obj, const FillLayer&
     return IntSize();
 }
 
+IntPoint accumulatedScrollOffset(const LayoutBoxModelObject& object, const LayoutBoxModelObject* container)
+{
+    const LayoutBlock* block = object.isLayoutBlock() ? toLayoutBlock(&object) : object.containingBlock();
+    IntPoint result;
+    while (block) {
+        if (block->hasOverflowClip())
+            result += block->scrolledContentOffset();
+        if (block == container)
+            break;
+        block = block->containingBlock();
+    }
+    return result;
+}
+
 } // anonymous namespace
 
 void BackgroundImageGeometry::setNoRepeatX(int xOffset)
@@ -223,12 +237,16 @@ void BackgroundImageGeometry::calculate(const LayoutBoxModelObject& obj, const L
         setHasNonLocalGeometry();
 
         IntRect viewportRect = pixelSnappedIntRect(obj.viewRect());
-        if (fixedBackgroundPaintsInLocalCoordinates(obj, globalPaintFlags))
+        if (fixedBackgroundPaintsInLocalCoordinates(obj, globalPaintFlags)) {
             viewportRect.setLocation(IntPoint());
-        else if (FrameView* frameView = obj.view()->frameView())
-            viewportRect.setLocation(frameView->scrollPosition());
+        } else {
+            if (FrameView* frameView = obj.view()->frameView())
+                viewportRect.setLocation(frameView->scrollPosition());
+            // Compensate the translations created by ScrollRecorders.
+            viewportRect.moveBy(accumulatedScrollOffset(obj, paintContainer));

[chrishtr, 2015/09/09 22:07:05]

Add a TODO(trchen) to fix this for SP phase 2, and note in the appropriate bug.

[Xianzhu, 2015/09/09 22:40:47]

Done.

+        }
 
-        if (paintContainer) {
+        if (paintContainer && paintContainer->view() == obj.view()) {

[chrishtr, 2015/09/09 22:07:05]

Why this change?

[Xianzhu, 2015/09/09 22:40:47]

Thought paintContainer could be in ancestor view of the current view. Debugged
and found that paintContainer will be the view even if the view is not
composited.

Removed the change.

             IntPoint absoluteContainerOffset = roundedIntPoint(paintContainer->localToAbsolute(FloatPoint()));
             viewportRect.moveBy(-absoluteContainerOffset);
         }