cc: More consistent reasoning about display list memory usage.

cc/playback/clip_path_display_item.cc

Index: cc/playback/clip_path_display_item.cc
diff --git a/cc/playback/clip_path_display_item.cc b/cc/playback/clip_path_display_item.cc
index 417b575701c8df892d1d3ce50bc92cbc7fb446cc..f7fd60626e5447738841624b8aa9a2c77a6a780b 100644
--- a/cc/playback/clip_path_display_item.cc
+++ b/cc/playback/clip_path_display_item.cc
@@ -23,9 +23,10 @@ void ClipPathDisplayItem::SetNew(const SkPath& clip_path,
   clip_op_ = clip_op;
   antialias_ = antialias;
 
-  size_t memory_usage = sizeof(SkPath) + sizeof(SkRegion::Op) + sizeof(bool);
+  // The size of SkPath's external storage is not currently accounted for (and
+  // may well be shared anyway).
   DisplayItem::SetNew(true /* suitable_for_gpu_raster */, 1 /* op_count */,
-                      memory_usage);
+                      0 /* external_memory_usage */);
 }
 
 void ClipPathDisplayItem::Raster(SkCanvas* canvas,
@@ -43,7 +44,7 @@ void ClipPathDisplayItem::AsValueInto(
 
 EndClipPathDisplayItem::EndClipPathDisplayItem() {
   DisplayItem::SetNew(true /* suitable_for_gpu_raster */, 0 /* op_count */,
-                      0 /* memory_usage */);
+                      0 /* external_memory_usage */);
 }
 
 EndClipPathDisplayItem::~EndClipPathDisplayItem() {