Added the framework for having canvas/recorder/picture record depth_set's.

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 426 matching lines @@
 
     /** Replace the current matrix with a copy of the specified matrix.
         @param matrix The matrix that will be copied into the current matrix.
     */
     void setMatrix(const SkMatrix& matrix);
 
     /** Helper for setMatrix(identity). Sets the current matrix to identity.
     */
     void resetMatrix();
 
+    /** Set the current draw depth of the canvas.

[robertphillips, 2016/07/08 17:26:43]

Fix this comment

[vjiaoblack, 2016/07/11 18:04:42]

Done.

+        @param z    The integer depth, intended between 0 - 255 inclusive
+                    0 is lowest (into screen), 255 is highest (out of screen)

[robertphillips, 2016/07/08 17:26:43]

Add info that this plays in the save/restore stack.

[vjiaoblack, 2016/07/11 18:04:42]

Done.

+    */
+    void setZ(SkScalar z);
+
+    /** Returns the current draw depth of the canvas.
+    */

[robertphillips, 2016/07/08 17:26:43]

Fix return value

[vjiaoblack, 2016/07/11 18:04:42]

Done.

+    uint32_t getZ() const;
+
     /**
      *  Modify the current clip with the specified rectangle.
      *  @param rect The rect to combine with the current clip
      *  @param op The region op to apply to the current clip
      *  @param doAntiAlias true if the clip should be antialiased
      */
     void clipRect(const SkRect& rect,
                   SkRegion::Op op = SkRegion::kIntersect_Op,
                   bool doAntiAlias = false);
 
@@ skipping 842 matching lines @@
     };
 
     virtual void willSave() {}
     // Overriders should call the corresponding INHERITED method up the inheritance chain.
     virtual SaveLayerStrategy getSaveLayerStrategy(const SaveLayerRec&) {
         return kFullLayer_SaveLayerStrategy;
     }
     virtual void willRestore() {}
     virtual void didRestore() {}
     virtual void didConcat(const SkMatrix&) {}
     virtual void didSetMatrix(const SkMatrix&) {}

[robertphillips, 2016/07/08 17:26:42]

don't need const on a scalar

[vjiaoblack, 2016/07/11 18:04:42]

Done.

+    virtual void didSetZ(const SkScalar) {}
 
     virtual void onDrawAnnotation(const SkRect&, const char key[], SkData* value);
     virtual void onDrawDRRect(const SkRRect&, const SkRRect&, const SkPaint&);
 
     virtual void onDrawText(const void* text, size_t byteLength, SkScalar x,
                             SkScalar y, const SkPaint& paint);
 
     virtual void onDrawPosText(const void* text, size_t byteLength,
                                const SkPoint pos[], const SkPaint& paint);
 
@@ skipping 265 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