cc: Make the PictureLayerImpl raster source null until commit.

cc/layers/picture_layer_impl.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 
@@ skipping 51 matching lines @@
 
 PictureLayerImpl::Pair::~Pair() {
 }
 
 PictureLayerImpl::PictureLayerImpl(LayerTreeImpl* tree_impl,
                                    int id,
                                    bool is_mask)
     : LayerImpl(tree_impl, id),
       twin_layer_(nullptr),
       tilings_(CreatePictureLayerTilingSet()),
-      // TODO(danakj): Can this be null to start?
-      raster_source_(PicturePileImpl::Create()),
       ideal_page_scale_(0.f),
       ideal_device_scale_(0.f),
       ideal_source_scale_(0.f),
       ideal_contents_scale_(0.f),
       raster_page_scale_(0.f),
       raster_device_scale_(0.f),
       raster_source_scale_(0.f),
       raster_contents_scale_(0.f),
       low_res_raster_contents_scale_(0.f),
       raster_source_scale_is_fixed_(false),
@@ skipping 489 matching lines @@
     scoped_refptr<RasterSource> raster_source,
     Region* new_invalidation,
     const PictureLayerTilingSet* pending_set) {
   // The bounds and the pile size may differ if the pile wasn't updated (ie.
   // PictureLayer::Update didn't happen). In that case the pile will be empty.
   DCHECK_IMPLIES(!raster_source->GetSize().IsEmpty(),
                  bounds() == raster_source->GetSize())
       << " bounds " << bounds().ToString() << " pile "
       << raster_source->GetSize().ToString();
 
-  bool could_have_tilings = CanHaveTilings();
+  // The |raster_source_| is initially null, so have to check for that for the
+  // first frame.
+  bool could_have_tilings = raster_source_.get() && CanHaveTilings();

[vmpstr, 2014/12/15 22:16:25]

nit: It would be cleaner, albeit slower, if this check was a part of
CanHaveTilings. I think this is fine, but give it a thought :P

[danakj, 2014/12/15 22:22:31]

I think I prefer it here, I want to be clear that code shouldn't be null
checking this in general, if you want to use the raster source and it's not
there you're doing something wrong, which I hope this comment and single
placement conveys.

   raster_source_.swap(raster_source);
 
   // The |new_invalidation| must be cleared before updating tilings since they
   // access the invalidation through the PictureLayerTilingClient interface.
   invalidation_.Clear();
   invalidation_.Swap(new_invalidation);
 
   bool can_have_tilings = CanHaveTilings();
 
   // Need to call UpdateTiles again if CanHaveTilings changed.
@@ skipping 717 matching lines @@
 
 bool PictureLayerImpl::AllTilesRequiredForDrawAreReadyToDraw() const {
   if (!layer_tree_impl()->IsActiveTree())
     return true;
 
   return AllTilesRequiredAreReadyToDraw(
       &PictureLayerTiling::IsTileRequiredForDrawIfVisible);
 }
 
 }  // namespace cc