cc: Documenting Layer APIs for transform offset, telemetry, tracing.

And remove an empty method and the caller on MicroBenchmark.

R=weiliangc@chromium.org

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I9750cbcf1daebf365f8e5bd91022dedf32e49ec4
Reviewed-on: https://chromium-review.googlesource.com/1103137
Commit-Queue: danakj <danakj@chromium.org>
Reviewed-by: weiliangc <weiliangc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568482}

cc/benchmarks/micro_benchmark.cc

@@ -34,8 +34,6 @@ void MicroBenchmark::NotifyDone(std::unique_ptr<base::Value> result) {
   is_done_ = true;
 }
 
-void MicroBenchmark::RunOnLayer(Layer* layer) {}
-
 void MicroBenchmark::RunOnLayer(PictureLayer* layer) {}
 
 bool MicroBenchmark::ProcessMessage(std::unique_ptr<base::Value> value) {

cc/benchmarks/micro_benchmark.h

@@ -16,11 +16,10 @@ class Value;
 }  // namespace base
 
 namespace cc {
-
-class Layer;
 class LayerTreeHost;
 class PictureLayer;
 class MicroBenchmarkImpl;
+
 class CC_EXPORT MicroBenchmark {
  public:
   using DoneCallback = base::OnceCallback<void(std::unique_ptr<base::Value>)>;
@@ -33,7 +32,6 @@ class CC_EXPORT MicroBenchmark {
   int id() const { return id_; }
   void set_id(int id) { id_ = id; }
 
-  virtual void RunOnLayer(Layer* layer);
   virtual void RunOnLayer(PictureLayer* layer);
 
   virtual bool ProcessMessage(std::unique_ptr<base::Value> value);

cc/layers/layer.cc

@@ -1394,9 +1394,7 @@ void Layer::AddDrawableDescendants(int num) {
     parent()->AddDrawableDescendants(num);
 }
 
-void Layer::RunMicroBenchmark(MicroBenchmark* benchmark) {
-  benchmark->RunOnLayer(this);
-}
+void Layer::RunMicroBenchmark(MicroBenchmark* benchmark) {}
 
 void Layer::SetElementId(ElementId id) {
   DCHECK(IsPropertyChangeAllowed());

cc/layers/layer.h

@@ -82,8 +82,15 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     SINGLE_TEXTURE_MASK,
   };
 
+  // Factory to create a new Layer, with a unique id.
   static scoped_refptr<Layer> Create();
 
+  // Sets an optional client on this layer, that will be called when relevant
+  // events happen. The client is a WeakPtr so it can be destroyed without
+  // unsetting itself as the client.
+  void SetLayerClient(base::WeakPtr<LayerClient> client);
+  LayerClient* GetLayerClientForTesting() const { return inputs_.client.get(); }
+
   // A unique and stable id for the Layer. Ids are always positive.
   int id() const { return inputs_.layer_id; }
 
@@ -540,13 +547,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
 
   void UpdateDebugInfo();
 
-  void SetLayerClient(base::WeakPtr<LayerClient> client);
-  LayerClient* GetLayerClientForTesting() const { return inputs_.client.get(); }
-
-  virtual sk_sp<SkPicture> GetPicture() const;
-
-  virtual void RunMicroBenchmark(MicroBenchmark* benchmark);
-
   // The index of this layer's node in the various property trees. These are
   // only valid after a main frame, when Update() is called on the layer, and
   // remain valid and in in the same state until the next main frame, or until
@@ -562,11 +562,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   void SetHasTransformNode(bool val) { has_transform_node_ = val; }
   bool has_transform_node() { return has_transform_node_; }
 
-  void SetOffsetToTransformParent(gfx::Vector2dF offset);
-  gfx::Vector2dF offset_to_transform_parent() const {
-    return offset_to_transform_parent_;
-  }
-
   void SetMayContainVideo(bool yes);
 
   // Stable identifier for clients. See comment in cc/trees/element_id.h.
@@ -594,6 +589,19 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   // Called on the scroll layer to trigger showing the overlay scrollbars.
   void ShowScrollbars() { needs_show_scrollbars_ = true; }
 
+  // For tracing. Gets a recorded rasterization of this layer's contents that
+  // can be displayed inside representations of this layer. May return null, in
+  // which case the layer won't be shown with any content in the tracing
+  // display.
+  virtual sk_sp<SkPicture> GetPicture() const;
+
+  // For telemetry testing. Runs a given test behaviour implemented in
+  // |benchmark| for this layer. The base class does nothing as benchmarks
+  // only exist for subclass layer types. For each subclass that the
+  // MicroBenchmark supports, the class should override this method and run the
+  // |benchmark| against this layer.
+  virtual void RunMicroBenchmark(MicroBenchmark* benchmark);
+
   // Internal method to create the compositor thread type for this Layer.
   // Subclasses should override this method if they want to return their own
   // subclass of LayerImpl instead.
@@ -674,6 +682,15 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   void SetEffectTreeIndex(int index);
   void SetScrollTreeIndex(int index);
 
+  // Internal to property tree construction. Set or get the position of this
+  // layer relative to the origin after transforming according to this layer's
+  // index into the transform tree. This translation is appended to the
+  // transform that comes from the transform tree for this layer.
+  void SetOffsetToTransformParent(gfx::Vector2dF offset);
+  gfx::Vector2dF offset_to_transform_parent() const {
+    return offset_to_transform_parent_;
+  }
+
   // Internal to property tree construction. Indicates that a property changed
   // on this layer that may affect the position or content of all layers in this
   // layer's subtree, including itself. This causes the layer's subtree to be