Add debug method to print surface references.

cc/surfaces/surface_manager.h

Index: cc/surfaces/surface_manager.h
diff --git a/cc/surfaces/surface_manager.h b/cc/surfaces/surface_manager.h
index b6885b81456a57a0ad6d6390afb37d5f71365e24..a43df1f6f5ab921b3e752aaeeb6c9e65b827db92 100644
--- a/cc/surfaces/surface_manager.h
+++ b/cc/surfaces/surface_manager.h
@@ -9,6 +9,8 @@
 
 #include <list>
 #include <memory>
+#include <sstream>

[danakj, 2017/01/17 23:21:57]

do u need more than iosfwd? and should these be inside DCHECK_IS_ON()?

[kylechar, 2017/01/18 15:06:18]

iosfwd has a forward def for stringstream, so it should be fine.

+#include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
@@ -43,6 +45,11 @@ class CC_SURFACES_EXPORT SurfaceManager
   explicit SurfaceManager(LifetimeType lifetime_type = LifetimeType::SEQUENCES);
   ~SurfaceManager() override;
 
+#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)

[danakj, 2017/01/17 23:21:57]

#if DCHECK_IS_ON() is the way to spell this

[kylechar, 2017/01/18 15:06:18]

Huh, that's handy.

+  // Returns a string representation of all reachable surface references.
+  std::string PrintSurfaceReferences();

[danakj, 2017/01/17 23:21:57]

This doesnt print, SurfaceReferencesToString ?

[kylechar, 2017/01/18 15:06:18]

Done.

+#endif
+
   void RegisterSurface(Surface* surface);
   void DeregisterSurface(const SurfaceId& surface_id);
 
@@ -126,6 +133,8 @@ class CC_SURFACES_EXPORT SurfaceManager
   }
 
  private:
+  using SurfaceIdSet = std::unordered_set<SurfaceId, SurfaceIdHash>;
+
   void RecursivelyAttachBeginFrameSource(const FrameSinkId& frame_sink_id,
                                          BeginFrameSource* source);
   void RecursivelyDetachBeginFrameSource(const FrameSinkId& frame_sink_id,
@@ -145,6 +154,13 @@ class CC_SURFACES_EXPORT SurfaceManager
   void RemoveSurfaceReferenceImpl(const SurfaceId& parent_id,
                                   const SurfaceId& child_id);
 
+#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
+  // Recursively prints surface references starting at |surface_id| to |str|.
+  void PrintSurfaceReferencesImpl(const SurfaceId& surface_id,
+                                  std::string indent,
+                                  std::stringstream* str);
+#endif
+
   // Use reference or sequence based lifetime management.
   LifetimeType lifetime_type_;
 
@@ -184,7 +200,6 @@ class CC_SURFACES_EXPORT SurfaceManager
   std::unordered_map<FrameSinkId, FrameSinkSourceMapping, FrameSinkIdHash>
       frame_sink_source_map_;
 
-  using SurfaceIdSet = std::unordered_set<SurfaceId, SurfaceIdHash>;
   // Tracks references from the child surface to parent surface. If there are
   // zero entries in the set for a SurfaceId then nothing is referencing the
   // surface and it can be garbage collected.