Remove some code now that forceCompositingMode is gone.

Source/core/rendering/compositing/RenderLayerCompositor.cpp

Index: Source/core/rendering/compositing/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.cpp b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
index e5223288835441e405264afd26c839289363d62d..3a447eaffe0486869d96eef592a887b07085dfc1 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -227,10 +227,7 @@ bool RenderLayerCompositor::acceleratedCompositingForOverflowScrollEnabled() con
 void RenderLayerCompositor::setCompositingLayersNeedRebuild()
 {
     // FIXME: crbug.com/332248 ideally this could be merged with setNeedsCompositingUpdate().
-    // FIXME: We can remove the staleInCompositingMode check once we get rid of the
-    // forceCompositingMode setting.
-    if (staleInCompositingMode())

[ojan, 2014/06/05 03:32:21]

Honestly, I can't remember why this was blocked on removing
forceCompositingMode. It caused some crazy codepath that shouldn't be possible
to happen. In either case, blocking setting this dirty bit on this stale value
doesn't make any sense.

-        m_compositingLayersNeedRebuild = true;
+    m_compositingLayersNeedRebuild = true;
     page()->animator().scheduleVisualUpdate();
     lifecycle().ensureStateAtMost(DocumentLifecycle::LayoutClean);
 }
@@ -471,13 +468,7 @@ bool RenderLayerCompositor::allocateOrClearCompositedLayerMapping(RenderLayer* l
     switch (compositedLayerUpdate) {
     case AllocateOwnCompositedLayerMapping:
         ASSERT(!layer->hasCompositedLayerMapping());
-        {
-            // FIXME: This can go away once we get rid of the forceCompositingMode setting.
-            // It's needed because setCompositingModeEnabled call ensureRootLayer, which
-            // eventually calls WebViewImpl::enterForceCompositingMode.
-            DeprecatedDirtyCompositingDuringCompositingUpdate marker(lifecycle());
-            setCompositingModeEnabled(true);
-        }
+        setCompositingModeEnabled(true);
 
         // If this layer was previously squashed, we need to remove its reference to a groupedMapping right away, so
         // that computing repaint rects will know the layer's correct compositingState.