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

src/core/SkCanvas.cpp

 /*
  * Copyright 2008 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.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkCanvas.h"
 #include "SkCanvasPriv.h"
@@ skipping 276 matching lines @@
         one that is at or below this level in the stack (so we know what
         bitmap/device to draw into from this level. This value is NOT
         reference counted, since the real owner is either our fLayer field,
         or a previous one in a lower level.)
     */
     DeviceCM*       fTopLayer;
     SkRasterClip    fRasterClip;
     SkMatrix        fMatrix;
     int             fDeferredSaveCount;
 
+    // This is the current cumulative depth (aggregate of all done translateZ calls)
+    SkScalar        fCurDrawDepth;
+
     MCRec(bool conservativeRasterClip) : fRasterClip(conservativeRasterClip) {
         fFilter     = nullptr;
         fLayer      = nullptr;
         fTopLayer   = nullptr;
         fMatrix.reset();
         fDeferredSaveCount = 0;
+        fCurDrawDepth      = 0;
 
         // don't bother initializing fNext
         inc_rec();
     }
-    MCRec(const MCRec& prev) : fRasterClip(prev.fRasterClip), fMatrix(prev.fMatrix) {
+    MCRec(const MCRec& prev) : fRasterClip(prev.fRasterClip), fMatrix(prev.fMatrix),
+                               fCurDrawDepth(prev.fCurDrawDepth) {
         fFilter = SkSafeRef(prev.fFilter);
         fLayer = nullptr;
         fTopLayer = prev.fTopLayer;
         fDeferredSaveCount = 0;
 
         // don't bother initializing fNext
         inc_rec();
     }
     ~MCRec() {
         SkSafeUnref(fFilter);
@@ skipping 1196 matching lines @@
 void SkCanvas::setMatrix(const SkMatrix& matrix) {
     this->checkForDeferredSave();
     this->internalSetMatrix(matrix);
     this->didSetMatrix(matrix);
 }
 
 void SkCanvas::resetMatrix() {
     this->setMatrix(SkMatrix::I());
 }
 
+void SkCanvas::translateZ(SkScalar z) {
+    this->checkForDeferredSave();
+    this->fMCRec->fCurDrawDepth += z;
+    this->didTranslateZ(z);
+}
+
+SkScalar SkCanvas::getZ() const {
+    return this->fMCRec->fCurDrawDepth;
+}
+
 //////////////////////////////////////////////////////////////////////////////
 
 void SkCanvas::clipRect(const SkRect& rect, SkRegion::Op op, bool doAA) {
     if (!fAllowSoftClip) {
         doAA = false;
     }
 
 #ifdef SK_SUPPORT_PRECHECK_CLIPRECT
     // Check if we can quick-accept the clip call (and do nothing)
     //
@@ skipping 1560 matching lines @@
 
 SkAutoCanvasMatrixPaint::~SkAutoCanvasMatrixPaint() {
     fCanvas->restoreToCount(fSaveCount);
 }
 
 #ifdef SK_SUPPORT_LEGACY_NEW_SURFACE_API
 SkSurface* SkCanvas::newSurface(const SkImageInfo& info, const SkSurfaceProps* props) {
     return this->makeSurface(info, props).release();
 }
 #endif