reduce alloc overhead for SkCanvas

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 1071 matching lines @@
         @return The current matrix on the canvas.
     */
     const SkMatrix& getTotalMatrix() const;
 
     /** Return the clip stack. The clip stack stores all the individual
      *  clips organized by the save/restore frame in which they were
      *  added.
      *  @return the current clip stack ("list" of individual clip elements)
      */
     const SkClipStack* getClipStack() const {
-        return fClipStack;
+        return &fClipStack;
     }
 
     typedef SkCanvasClipVisitor ClipVisitor;
     /**
      *  Replays the clip operations, back to front, that have been applied to
      *  the canvas, calling the appropriate method on the visitor for each
      *  clip. All clips have already been transformed into device space.
      */
     void replayClips(ClipVisitor*) const;
 
@@ skipping 141 matching lines @@
                         SkIRect* intersection,
                         const SkImageFilter* imageFilter = NULL);
 
     // notify our surface (if we have one) that we are about to draw, so it
     // can perform copy-on-write or invalidate any cached images
     void predrawNotify();
 
 private:
     class MCRec;
 
-    SkAutoTUnref<SkClipStack> fClipStack;
+    SkClipStack fClipStack;
     SkDeque     fMCStack;
     // points to top of stack
     MCRec*      fMCRec;
     // the first N recs that can fit here mean we won't call malloc
-    uint32_t    fMCRecStorage[32];
+    enum {
+        kMCRecSize  = 128,   // most recent measurement
+        kMCRecCount = 8,     // common depth for save/restores
+    };
+    intptr_t fMCRecStorage[kMCRecSize * kMCRecCount / sizeof(intptr_t)];
+    // for our base DeviceCM
+    intptr_t fBaseLayerStorage[kMCRecSize / sizeof(intptr_t)];
 
     const SkSurfaceProps fProps;
 
     int         fSaveCount;         // value returned by getSaveCount()
 
     SkMetaData* fMetaData;
 
     SkSurface_Base*  fSurfaceBase;
     SkSurface_Base* getSurfaceBase() const { return fSurfaceBase; }
     void setSurfaceBase(SkSurface_Base* sb) {
@@ skipping 220 matching lines @@
 
 class SkCanvasClipVisitor {
 public:
     virtual ~SkCanvasClipVisitor();
     virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
 };
 
 #endif