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

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index ec14829ca85296d12d79d27a04073c6ee587c20e..3f399a8234beafec6b6ca27f0b3fa97eb03ccd37 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -444,6 +444,19 @@ public:
     */
     void resetMatrix();
 
+    /** Set the current draw depth of the canvas.
+        @param z    The SkScalar depth; it's tracked in the save/restore stack.
+                    Negative into screen, positive out of screen.
+                    Defaults to 0.
+    */
+    void translateZ(SkScalar z);
+
+protected:

[bsalomon, 2016/07/12 15:26:34]

We usually try to just have one public, protected and private section in each
class. Could move this below?

[robertphillips, 2016/07/12 15:34:32]

add the word "cumulative" somewhere here ?

[vjiaoblack, 2016/07/12 16:03:33]

Sure, but I think that's redundant!

+    /** Returns the current draw depth of the canvas.
+    */
+    SkScalar getZ() const;
+public:
+
     /**
      *  Modify the current clip with the specified rectangle.
      *  @param rect The rect to combine with the current clip
@@ -1307,6 +1320,7 @@ protected:
     virtual void didRestore() {}
     virtual void didConcat(const SkMatrix&) {}
     virtual void didSetMatrix(const SkMatrix&) {}
+    virtual void didTranslateZ(SkScalar) {}
 
     virtual void onDrawAnnotation(const SkRect&, const char key[], SkData* value);
     virtual void onDrawDRRect(const SkRRect&, const SkRRect&, const SkPaint&);