Clip nodes to the visible rect.

Do not build scrollable layers if the layer does not draw. No need to ask for a
sync since the rebuild happens during a sync.

Bug: 3429982
Change-Id: I7740cd4de4e1658e760da7391de708cbdf05cd44

2 files changed, 28 insertions, 3 deletions

diff --git a/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp b/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
index 49f20ab..ccc872a 100644
--- a/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
+++ b/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
@@ -467,7 +467,7 @@ void GraphicsLayerAndroid::updateScrollingLayers()
 {
 #if ENABLE(ANDROID_OVERFLOW_SCROLL)
     RenderLayer* layer = renderLayerFromClient(m_client);
-    if (!layer)
+    if (!layer || !m_haveContents)
         return;
     bool hasOverflowScroll = m_foregroundLayer || m_contentLayer->contentIsScrollable();
     bool layerNeedsOverflow = layer->hasOverflowScroll();
@@ -508,7 +508,6 @@ void GraphicsLayerAndroid::updateScrollingLayers()
         }
         // Need to rebuild our children based on the new structure.
         m_needsSyncChildren = true;
-        askForSync();
     } else {
         ASSERT(hasOverflowScroll && !layerNeedsOverflow && !iframeNeedsOverflow);
         ASSERT(m_contentLayer);
@@ -531,7 +530,6 @@ void GraphicsLayerAndroid::updateScrollingLayers()
         }
         // Children are all re-parented.
         m_needsSyncChildren = true;
-        askForSync();
     }
 #endif
 }
diff --git a/WebKit/android/nav/CachedLayer.cpp b/WebKit/android/nav/CachedLayer.cpp
index d5385bd..3321797 100644
--- a/WebKit/android/nav/CachedLayer.cpp
+++ b/WebKit/android/nav/CachedLayer.cpp
@@ -55,9 +55,36 @@ IntRect CachedLayer::adjustBounds(const LayerAndroid* root,
     temp.move(position.x(), position.y());
 
     // Add in any layer translation.
+    // FIXME: Should use bounds() and apply the entire transformation matrix.
     const FloatPoint& translation = aLayer->translation();
     temp.move(translation.x(), translation.y());
 
+    SkRect clip;
+    aLayer->bounds(&clip);
+
+    // Do not try to traverse the parent chain if this is the root as the parent
+    // will not be a LayerAndroid.
+    if (aLayer != root) {
+        LayerAndroid* parent = static_cast<LayerAndroid*>(aLayer->getParent());
+        while (parent) {
+            SkRect pClip;
+            parent->bounds(&pClip);
+
+            // Move our position into our parent's coordinate space.
+            clip.offset(pClip.fLeft, pClip.fTop);
+            // Clip our visible rectangle to the parent.
+            clip.intersect(pClip);
+
+            // Stop at the root.
+            if (parent == root)
+                break;
+            parent = static_cast<LayerAndroid*>(parent->getParent());
+        }
+    }
+
+    // Intersect the result with the visible clip.
+    temp.intersect(clip);
+
     IntRect result = enclosingIntRect(temp);
 
     DBG_NAV_LOGV("root=%p aLayer=%p [%d]"