cc: Fix PictureLayerImpl crash in post-commit init

If the post-commit initialization happens during the first activation,
there's a crash when trying to sync to an existing but uninitialized
active layer.  Fix this by checking for this case.

R=danakj@chromium.org
BUG=267144

Review URL: https://chromiumcodereview.appspot.com/21632002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@215188 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 49 insertions, 1 deletions

diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 1e2b5c2..a5c69cc 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -527,6 +527,9 @@ gfx::Size PictureLayerImpl::CalculateTileSize(
 }
 
 void PictureLayerImpl::SyncFromActiveLayer(const PictureLayerImpl* other) {
+  DCHECK(!other->needs_post_commit_initialization_);
+  DCHECK(other->tilings_);
+
   UpdateLCDTextStatus(other->is_using_lcd_text_);
 
   if (!DrawsContent()) {
@@ -722,7 +725,10 @@ void PictureLayerImpl::DoPostCommitInitialization() {
   if (twin_layer_) {
     DCHECK(!twin_layer_->twin_layer_);
     twin_layer_->twin_layer_ = this;
-    SyncFromActiveLayer(twin_layer_);
+    // If the twin has never been pushed to, do not sync from it.
+    // This can happen if this function is called during activation.
+    if (!twin_layer_->needs_post_commit_initialization_)
+      SyncFromActiveLayer(twin_layer_);
   }
 
   needs_post_commit_initialization_ = false;
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index d800123..3272712 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -1006,5 +1006,40 @@ TEST_F(PictureLayerImplTest, MarkRequiredOffscreenTiles) {
   EXPECT_GT(num_offscreen, 0);
 }
 
+TEST_F(PictureLayerImplTest, ActivateUninitializedLayer) {
+  gfx::Size tile_size(100, 100);
+  gfx::Size layer_bounds(400, 400);
+  scoped_refptr<FakePicturePileImpl> pending_pile =
+      FakePicturePileImpl::CreateFilledPile(tile_size, layer_bounds);
+
+  host_impl_.CreatePendingTree();
+  LayerTreeImpl* pending_tree = host_impl_.pending_tree();
+
+  scoped_ptr<FakePictureLayerImpl> pending_layer =
+      FakePictureLayerImpl::CreateWithPile(pending_tree, id_, pending_pile);
+  pending_layer->SetDrawsContent(true);
+  pending_tree->SetRootLayer(pending_layer.PassAs<LayerImpl>());
+
+  pending_layer_ = static_cast<FakePictureLayerImpl*>(
+      host_impl_.pending_tree()->LayerById(id_));
+
+  // Set some state on the pending layer, make sure it is not clobbered
+  // by a sync from the active layer.  This could happen because if the
+  // pending layer has not been post-commit initialized it will attempt
+  // to sync from the active layer.
+  bool default_lcd_text_setting = pending_layer_->is_using_lcd_text();
+  pending_layer_->force_set_lcd_text(!default_lcd_text_setting);
+  EXPECT_TRUE(pending_layer_->needs_post_commit_initialization());
+
+  host_impl_.ActivatePendingTree();
+
+  active_layer_ = static_cast<FakePictureLayerImpl*>(
+      host_impl_.active_tree()->LayerById(id_));
+
+  EXPECT_EQ(0u, active_layer_->num_tilings());
+  EXPECT_EQ(!default_lcd_text_setting, active_layer_->is_using_lcd_text());
+  EXPECT_FALSE(active_layer_->needs_post_commit_initialization());
+}
+
 }  // namespace
 }  // namespace cc
diff --git a/cc/test/fake_picture_layer_impl.h b/cc/test/fake_picture_layer_impl.h
index 248437b..2eeaeef 100644
--- a/cc/test/fake_picture_layer_impl.h
+++ b/cc/test/fake_picture_layer_impl.h
@@ -34,6 +34,13 @@ class FakePictureLayerImpl : public PictureLayerImpl {
   using PictureLayerImpl::MarkVisibleResourcesAsRequired;
   using PictureLayerImpl::DoPostCommitInitializationIfNeeded;
 
+  bool needs_post_commit_initialization() const {
+    return needs_post_commit_initialization_;
+  }
+
+  bool is_using_lcd_text() const { return is_using_lcd_text_; }
+  void force_set_lcd_text(bool enabled) { is_using_lcd_text_ = enabled; }
+
   PictureLayerTiling* HighResTiling() const;
   PictureLayerTiling* LowResTiling() const;
   size_t num_tilings() const { return tilings_->num_tilings(); }