Bug 699351. Add nsIFrameLoader::clipSubdocument API to allow XUL <iframe> and <browser> to not clip the subdocument. r=tnikkel,sr=bzbarsky

layout/generic/nsFrame.cpp

@@ -6439,13 +6439,17 @@ nsFrame::CreateAccessible()
 NS_DECLARE_FRAME_PROPERTY(OverflowAreasProperty,
                           nsIFrame::DestroyOverflowAreas)
 
-void
+bool
 nsIFrame::ClearOverflowRects()
 {
+  if (mOverflow.mType == NS_FRAME_OVERFLOW_NONE) {
+    return false;
+  }
   if (mOverflow.mType == NS_FRAME_OVERFLOW_LARGE) {
     Properties().Delete(OverflowAreasProperty());
   }
   mOverflow.mType = NS_FRAME_OVERFLOW_NONE;
+  return true;
 }
 
 /** Create or retrieve the previously stored overflow area, if the frame does 
@@ -6473,17 +6477,18 @@ nsIFrame::GetOverflowAreasProperty()
 /** Set the overflowArea rect, storing it as deltas or a separate rect
  * depending on its size in relation to the primary frame rect.
  */
-void
+bool
 nsIFrame::SetOverflowAreas(const nsOverflowAreas& aOverflowAreas)
 {
   if (mOverflow.mType == NS_FRAME_OVERFLOW_LARGE) {
     nsOverflowAreas *overflow =
       static_cast<nsOverflowAreas*>(Properties().Get(OverflowAreasProperty()));
+    bool changed = *overflow != aOverflowAreas;
     *overflow = aOverflowAreas;
 
     // Don't bother with converting to the deltas form if we already
     // have a property.
-    return;
+    return changed;
   }
 
   const nsRect& vis = aOverflowAreas.VisualOverflow();
@@ -6505,6 +6510,7 @@ nsIFrame::SetOverflowAreas(const nsOverflowAreas& aOverflowAreas)
       // so that our eventual SetRect/SetSize will know that it has to
       // reset our overflow areas.
       (l | t | r | b) != 0) {
+    VisualDeltas oldDeltas = mOverflow.mVisualDeltas;
     // It's a "small" overflow area so we store the deltas for each edge
     // directly in the frame, rather than allocating a separate rect.
     // If they're all zero, that's fine; we're setting things to
@@ -6513,12 +6519,18 @@ nsIFrame::SetOverflowAreas(const nsOverflowAreas& aOverflowAreas)
     mOverflow.mVisualDeltas.mTop    = t;
     mOverflow.mVisualDeltas.mRight  = r;
     mOverflow.mVisualDeltas.mBottom = b;
+    // There was no scrollable overflow before, and there isn't now.
+    return oldDeltas != mOverflow.mVisualDeltas;
   } else {
+    bool changed = !aOverflowAreas.ScrollableOverflow().IsEqualEdges(nsRect(nsPoint(0, 0), GetSize())) ||
+      !aOverflowAreas.VisualOverflow().IsEqualEdges(GetVisualOverflowFromDeltas());
+
     // it's a large overflow area that we need to store as a property
     mOverflow.mType = NS_FRAME_OVERFLOW_LARGE;
     nsOverflowAreas* overflow = GetOverflowAreasProperty();
     NS_ASSERTION(overflow, "should have created areas");
     *overflow = aOverflowAreas;
+    return changed;
   }
 }
 
@@ -6529,7 +6541,7 @@ IsInlineFrame(nsIFrame *aFrame)
   return type == nsGkAtoms::inlineFrame;
 }
 
-void 
+bool
 nsIFrame::FinishAndStoreOverflow(nsOverflowAreas& aOverflowAreas,
                                  nsSize aNewSize)
 {
@@ -6638,11 +6650,11 @@ nsIFrame::FinishAndStoreOverflow(nsOverflowAreas& aOverflowAreas,
 
   bool visualOverflowChanged =
     !GetVisualOverflowRect().IsEqualInterior(aOverflowAreas.VisualOverflow());
-
+  bool anyOverflowChanged;
   if (aOverflowAreas != nsOverflowAreas(bounds, bounds)) {
-    SetOverflowAreas(aOverflowAreas);
+    anyOverflowChanged = SetOverflowAreas(aOverflowAreas);
   } else {
-    ClearOverflowRects();
+    anyOverflowChanged = ClearOverflowRects();
   }
 
   if (visualOverflowChanged) {
@@ -6687,6 +6699,8 @@ nsIFrame::FinishAndStoreOverflow(nsOverflowAreas& aOverflowAreas,
                       nsDisplayItem::TYPE_TRANSFORM);
     }
   }
+
+  return anyOverflowChanged;
 }
 
 /* The overflow rects for leaf nodes in a preserve-3d hierarchy depends on