cc: Don't add tilings to layers without recordings.

Before calling PictureLayerImpl::AddTiling() the layer checks to
make sure it has a recording, as this should be an invariant for
adding a tiling. Code paths to sync tilings were not checking this
however, and causing DCHECKs to fire as a result.

Any time we add a tiling, we must check that we are able to do so
by verifying:
1) The contents scale of the tiling is large enough.
2) The layer has a recording (and is non-empty).
3) The layer DrawsContents()

The first was already verified, the second was not, and the third
was only in some situations.

R=enne
BUG=240361

Review URL: https://chromiumcodereview.appspot.com/14813034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@200205 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 29 insertions, 7 deletions

diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 8c50b94..00bb878 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -548,13 +548,15 @@ void PictureLayerImpl::SyncFromActiveLayer(const PictureLayerImpl* other) {
   invalidation_.Union(difference_region);
 
   tilings_->RemoveAllTilings();
-  tilings_->AddTilingsToMatchScales(*other->tilings_, MinimumContentsScale());
+  if (CanHaveTilings())
+    tilings_->AddTilingsToMatchScales(*other->tilings_, MinimumContentsScale());
+
   DCHECK(bounds() == tilings_->layer_bounds());
 }
 
 void PictureLayerImpl::SyncTiling(
     const PictureLayerTiling* tiling) {
-  if (!DrawsContent() || tiling->contents_scale() < MinimumContentsScale())
+  if (!CanHaveTilingWithScale(tiling->contents_scale()))
     return;
   tilings_->AddTiling(tiling->contents_scale());
 
@@ -652,7 +654,8 @@ bool PictureLayerImpl::AreVisibleResourcesReady() const {
 }
 
 PictureLayerTiling* PictureLayerImpl::AddTiling(float contents_scale) {
-  DCHECK(contents_scale >= MinimumContentsScale());
+  DCHECK(CanHaveTilingWithScale(contents_scale)) <<
+      "contents_scale: " << contents_scale;
 
   PictureLayerTiling* tiling = tilings_->AddTiling(contents_scale);
 
@@ -703,7 +706,7 @@ void PictureLayerImpl::ManageTilings(bool animating_transform_to_screen) {
   DCHECK(ideal_device_scale_);
   DCHECK(ideal_source_scale_);
 
-  if (pile_->recorded_region().IsEmpty())
+  if (!CanHaveTilings())
     return;
 
   bool change_target_tiling =
@@ -943,6 +946,22 @@ void PictureLayerImpl::ResetRasterScale() {
   low_res_raster_contents_scale_ = 0.f;
 }
 
+bool PictureLayerImpl::CanHaveTilings() const {
+  if (!DrawsContent())
+    return false;
+  if (pile_->recorded_region().IsEmpty())
+    return false;
+  return true;
+}
+
+bool PictureLayerImpl::CanHaveTilingWithScale(float contents_scale) const {
+  if (!CanHaveTilings())
+    return false;
+  if (contents_scale < MinimumContentsScale())
+    return false;
+  return true;
+}
+
 void PictureLayerImpl::GetDebugBorderProperties(
     SkColor* color,
     float* width) const {
diff --git a/cc/layers/picture_layer_impl.h b/cc/layers/picture_layer_impl.h
index 736ba60..f982ea8 100644
--- a/cc/layers/picture_layer_impl.h
+++ b/cc/layers/picture_layer_impl.h
@@ -94,6 +94,9 @@ class CC_EXPORT PictureLayerImpl
   void UpdateLCDTextStatus();
   void ResetRasterScale();
 
+  bool CanHaveTilings() const;
+  bool CanHaveTilingWithScale(float contents_scale) const;
+
   virtual void GetDebugBorderProperties(
       SkColor* color, float* width) const OVERRIDE;
   virtual void AsValueInto(base::DictionaryValue* dict) const OVERRIDE;
diff --git a/cc/resources/picture_layer_tiling.cc b/cc/resources/picture_layer_tiling.cc
index 678a0fa..1a041f2 100644
--- a/cc/resources/picture_layer_tiling.cc
+++ b/cc/resources/picture_layer_tiling.cc
@@ -44,9 +44,9 @@ PictureLayerTiling::PictureLayerTiling(float contents_scale,
 
   DCHECK(!gfx::ToFlooredSize(
       gfx::ScaleSize(layer_bounds, contents_scale)).IsEmpty()) <<
-      "Tiling created with scale too small as contents become empty. " <<
-      "Layer bounds: " << layer_bounds.ToString() <<
-      "Contents scale: " << contents_scale;
+      "Tiling created with scale too small as contents become empty." <<
+      " Layer bounds: " << layer_bounds.ToString() <<
+      " Contents scale: " << contents_scale;
 
   tiling_data_.SetTotalSize(content_bounds);
   tiling_data_.SetMaxTextureSize(tile_size);