Fix position update

We fixed two issues here.
First, when fixed left/right both undefined, the renderlayer position already
took the fix margin into consideration, so we don't need to compute that again.

Second, for compute the fix element's ViewRect, we just need the normal width,
not the overflow one.

bug:4440999
Change-Id: I664c64688a89579f0023288185772c61b01c7cc8

1 files changed, 7 insertions, 9 deletions

diff --git a/Source/WebCore/platform/graphics/android/LayerAndroid.cpp b/Source/WebCore/platform/graphics/android/LayerAndroid.cpp
index 7bef420..95ccedc 100644
--- a/Source/WebCore/platform/graphics/android/LayerAndroid.cpp
+++ b/Source/WebCore/platform/graphics/android/LayerAndroid.cpp
@@ -540,21 +540,19 @@ void LayerAndroid::updateFixedLayersPositions(SkRect viewport, LayerAndroid* par
         float x = dx;
         float y = dy;
 
-        // It turns out that when it is 'auto', the webkit computation will
-        // take one more factor into account,  that is the original render
-        // layer's X,Y, such that it will align well with the parent's layer.
+        // It turns out that when it is 'auto', we should use the webkit value
+        // from the original render layer's X,Y, that will take care of alignment
+        // with the parent's layer and fix Margin etc.
         if (!(m_fixedLeft.defined() || m_fixedRight.defined()))
             x += m_renderLayerPos.x();
-
-        if (!(m_fixedTop.defined() || m_fixedBottom.defined()))
-            y += m_renderLayerPos.y();
-
-        if (m_fixedLeft.defined() || !m_fixedRight.defined())
+        else if (m_fixedLeft.defined() || !m_fixedRight.defined())
             x += m_fixedMarginLeft.calcFloatValue(w) + m_fixedLeft.calcFloatValue(w) - m_fixedRect.fLeft;
         else
             x += w - m_fixedMarginRight.calcFloatValue(w) - m_fixedRight.calcFloatValue(w) - m_fixedRect.fRight;
 
-        if (m_fixedTop.defined() || !m_fixedBottom.defined())
+        if (!(m_fixedTop.defined() || m_fixedBottom.defined()))
+            y += m_renderLayerPos.y();
+        else if (m_fixedTop.defined() || !m_fixedBottom.defined())
             y += m_fixedMarginTop.calcFloatValue(h) + m_fixedTop.calcFloatValue(h) - m_fixedRect.fTop;
         else
             y += h - m_fixedMarginBottom.calcFloatValue(h) - m_fixedBottom.calcFloatValue(h) - m_fixedRect.fBottom;