5 files changed, 41 insertions, 31 deletions

diff --git a/WebCore/page/FrameView.cpp b/WebCore/page/FrameView.cpp
index bac995d..17ba2bc 100644
--- a/WebCore/page/FrameView.cpp
+++ b/WebCore/page/FrameView.cpp
@@ -555,16 +555,9 @@ void FrameView::updateCompositingLayers()
     if (!view)
         return;
 #if ENABLE(ANDROID_OVERFLOW_SCROLL)
-    // Enter compositing mode for child frames that have layout dimensions.  The
-    // decision to enable compositing for the RenderView will be done in the
-    // compositor.
-    if (false && m_frame->ownerRenderer() && (layoutWidth() | layoutHeight()) && !view->usesCompositing()) {
-        ScrollbarMode h,v;
-        scrollbarModes(h, v);
-        if ((h != ScrollbarAlwaysOff && layoutWidth() < contentsWidth()) ||
-            (v != ScrollbarAlwaysOff && layoutHeight() < contentsHeight()))
-            enterCompositingMode();
-    }
+    // Enter compositing mode for child frames that have layout dimensions.
+    if (hasOverflowScroll())
+        enterCompositingMode();
 #endif
 
     // This call will make sure the cached hasAcceleratedCompositing is updated from the pref
@@ -579,6 +572,28 @@ void FrameView::setNeedsOneShotDrawingSynchronization()
         page->chrome()->client()->setNeedsOneShotDrawingSynchronization();
 }
 
+#if ENABLE(ANDROID_OVERFLOW_SCROLL)
+bool FrameView::hasOverflowScroll() const
+{
+    RenderObject* ownerRenderer = m_frame->ownerRenderer();
+    if (!ownerRenderer || !ownerRenderer->isRenderIFrame())
+        return false;
+    RenderLayer* layer = ownerRenderer->enclosingLayer();
+    // Make sure the layer has visible content or descendants.
+    if (!layer->hasVisibleContent() && !layer->hasVisibleDescendant())
+        return false;
+    // If either layout dimension is 0, return false.
+    if (!layoutWidth() || !layoutHeight())
+        return false;
+    ScrollbarMode h, v;
+    scrollbarModes(h, v);
+    if (h == ScrollbarAlwaysOff || v == ScrollbarAlwaysOff)
+        return false;
+    if (contentsWidth() <= layoutWidth() && contentsHeight() <= layoutHeight())
+        return false;
+    return true;
+}
+#endif
 #endif // USE(ACCELERATED_COMPOSITING)
 
 bool FrameView::hasCompositedContent() const
diff --git a/WebCore/page/FrameView.h b/WebCore/page/FrameView.h
index 8a1a071..87924b2 100644
--- a/WebCore/page/FrameView.h
+++ b/WebCore/page/FrameView.h
@@ -104,6 +104,9 @@ public:
     // Called when changes to the GraphicsLayer hierarchy have to be synchronized with
     // content rendered via the normal painting path.
     void setNeedsOneShotDrawingSynchronization();
+#if ENABLE(ANDROID_OVERFLOW_SCROLL)
+    bool hasOverflowScroll() const;
+#endif
 #endif
 
     bool hasCompositedContent() const;
diff --git a/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp b/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
index 2fa1215..d99c1cb 100644
--- a/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
+++ b/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
@@ -373,10 +373,15 @@ void GraphicsLayerAndroid::setDrawsContent(bool drawsContent)
                 m_contentLayer->addChild(m_foregroundClipLayer);
             } else if (layer->isRootLayer()
                        && layer->renderer()->frame()->ownerRenderer()) {
-                // Replace the content layer with a scrollable layer.
-                LayerAndroid* layer = new ScrollableLayerAndroid(*m_contentLayer);
-                m_contentLayer->unref();
-                m_contentLayer = layer;
+                // We have to do another check for scrollable content since an
+                // iframe might be compositing for other reasons.
+                FrameView* view = layer->renderer()->frame()->view();
+                if (view->hasOverflowScroll()) {
+                    // Replace the content layer with a scrollable layer.
+                    LayerAndroid* layer = new ScrollableLayerAndroid(*m_contentLayer);
+                    m_contentLayer->unref();
+                    m_contentLayer = layer;
+                }
             }
         }
 #endif
diff --git a/WebCore/rendering/RenderLayer.cpp b/WebCore/rendering/RenderLayer.cpp
index 9d894af..2d2559c 100644
--- a/WebCore/rendering/RenderLayer.cpp
+++ b/WebCore/rendering/RenderLayer.cpp
@@ -2159,8 +2159,9 @@ RenderLayer::updateScrollInfoAfterLayout()
 #if ENABLE(ANDROID_OVERFLOW_SCROLL)
     if (hasOverflowScroll()) {
         rendererContentChanged();
+        if (parent())
+            parent()->dirtyNormalFlowList();
         dirtyStackingContextZOrderLists();
-        dirtyZOrderLists();
     }
 #endif
 }
diff --git a/WebCore/rendering/RenderLayerCompositor.cpp b/WebCore/rendering/RenderLayerCompositor.cpp
index c6cd277..e6ea32a 100644
--- a/WebCore/rendering/RenderLayerCompositor.cpp
+++ b/WebCore/rendering/RenderLayerCompositor.cpp
@@ -1176,22 +1176,8 @@ bool RenderLayerCompositor::requiresCompositingForMobileSites(const RenderLayer*
 #if ENABLE(ANDROID_OVERFLOW_SCROLL)
     if (layer->hasOverflowScroll())
         return true;
-    HTMLFrameOwnerElement* ownerElement = enclosingIFrameElement();
-    RenderObject* renderer = ownerElement ? ownerElement->renderer() : 0;
-    if (false && layer->isRootLayer() && renderer && renderer->isRenderIFrame()) {
-        if (layer->renderer()->frame()) {
-            FrameView* view = layer->renderer()->frame()->view();
-            if (view) {
-                // Enable compositing if the frame can scroll and the contents
-                // are larger than the layout dimensions.
-                ScrollbarMode h,v;
-                view->scrollbarModes(h, v);
-                if ((h != ScrollbarAlwaysOff && view->layoutWidth() < view->contentsWidth()) ||
-                    (v != ScrollbarAlwaysOff && view->layoutHeight() < view->contentsHeight()))
-                    return true;
-            }
-        }
-    }
+    if (layer->isRootLayer() && m_renderView->frameView()->hasOverflowScroll())
+        return true;
 #endif
 #if ENABLE(COMPOSITED_FIXED_ELEMENTS)
     // First, check if we are in an iframe, and if so bail out