Bug 831973 - Remove extra scroll compensation code; r=roc

gfx/layers/ipc/CompositorParent.cpp

@@ -526,8 +526,6 @@ private:
             if (AsyncPanZoomController* apzc = state->mController) {
               referent->SetUserData(&sPanZoomUserDataKey,
                                     new PanZoomUserData(apzc));
-            } else {
-              CompensateForContentScrollOffset(ref, referent);
             }
           } else {
             ref->DetachReferentLayer(referent);
@@ -542,31 +540,6 @@ private:
     }
   }
 
-  // XXX the fact that we have to do this evidence of bad API design.
-  void CompensateForContentScrollOffset(Layer* aContainer,
-                                        Layer* aShadowContent)
-  {
-    ContainerLayer* c = aShadowContent->AsContainerLayer();
-    if (!c) {
-      return;
-    }
-    const FrameMetrics& fm = c->GetFrameMetrics();
-    gfx3DMatrix m(aContainer->GetTransform());
-    m.Translate(gfxPoint3D(-fm.GetScrollOffsetInLayerPixels().x,
-                           -fm.GetScrollOffsetInLayerPixels().y, 0));
-
-    // The transform already takes the resolution scale into account.  Since we
-    // will apply the resolution scale again when computing the effective
-    // transform, we must apply the inverse resolution scale here.
-    m.Scale(1.0f/c->GetPreXScale(),
-            1.0f/c->GetPreYScale(),
-            1);
-    m.ScalePost(1.0f/c->GetPostXScale(),
-                1.0f/c->GetPostYScale(),
-                1);
-    aContainer->AsShadowLayer()->SetShadowTransform(m);
-  }
-
   bool IsSameDimension(ScreenOrientation o1, ScreenOrientation o2) {
     bool isO1portrait = (o1 == eScreenOrientation_PortraitPrimary || o1 == eScreenOrientation_PortraitSecondary);
     bool isO2portrait = (o2 == eScreenOrientation_PortraitPrimary || o2 == eScreenOrientation_PortraitSecondary);