Use variable length key (rather than accumulated matrix) as save layer hoisting key

src/core/SkLayerInfo.h

Index: src/core/SkLayerInfo.h
diff --git a/src/core/SkLayerInfo.h b/src/core/SkLayerInfo.h
index dd0eaf032ab8bc901be86665b7a221101bfcdd66..196f1b93af3b910d327ba84e050fd875dc545212 100644
--- a/src/core/SkLayerInfo.h
+++ b/src/core/SkLayerInfo.h
@@ -18,8 +18,8 @@ public:
     // Information about a given saveLayer/restore block in an SkPicture
     class BlockInfo {
     public:
-        BlockInfo() : fPicture(NULL), fPaint(NULL) {}
-        ~BlockInfo() { SkSafeUnref(fPicture); SkDELETE(fPaint); }
+        BlockInfo() : fPicture(NULL), fPaint(NULL), fKey(NULL), fKeySize(0) {}
+        ~BlockInfo() { SkSafeUnref(fPicture); SkDELETE(fPaint); SkDELETE_ARRAY(fKey); }
 
         // The picture owning the layer. If the owning picture is the top-most
         // one (i.e., the picture for which this SkLayerInfo was created) then
@@ -50,6 +50,10 @@ public:
         bool    fHasNestedLayers;
         // True if this saveLayer is nested within another. False otherwise.
         bool    fIsNested;
+        // The variable length key for this saveLayer block. It stores the
+        // thread of operation indices that lead the saveLayer operation.
+        int*    fKey;

[bsalomon, 2014/11/25 13:52:05]

Did you consider using SkAutoSTArray here? (It's a fixed -ized dyn-allocated
array, unlike similarly named SkSTArray).

[robertphillips, 2014/11/25 16:36:47]

SkAutoTArray would work if it had a count in Release. In this instance I always
know the size of fKey when allocating it, it doesn't change and the contents are
POD so SkAutoSTArray is somewhat overkill.

+        int     fKeySize;  // # of ints
     };
 
     SkLayerInfo(Key key) : INHERITED(key) { }