add heuristic to pour small pictures into recordings, rather than ref'ing

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 "SkCanvas.h"
 #include "SkCanvasPriv.h"
 #include "SkBitmapDevice.h"
@@ skipping 2490 matching lines @@
                                 const SkPath& path, SkScalar hOffset,
                                 SkScalar vOffset, const SkPaint& paint) {
     TRACE_EVENT0("disabled-by-default-skia", "SkCanvas::drawTextOnPathHV()");
     SkMatrix    matrix;
 
     matrix.setTranslate(hOffset, vOffset);
     this->drawTextOnPath(text, byteLength, path, &matrix, paint);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
-void SkCanvas::drawPicture(const SkPicture* picture) {
-    TRACE_EVENT0("disabled-by-default-skia", "SkCanvas::drawPicture()");
-    if (picture) {
-        this->onDrawPicture(picture, NULL, NULL);
-    }
-}
+
+/**
+ *  This constant is trying to balance the speed of ref'ing a subpicture into a parent picture,
+ *  against the playback cost of recursing into the subpicture to get at its actual ops.
+ *
+ *  For now we pick a conservatively small value, though measurement (and other heuristics like
+ *  the type of ops contained) may justify changing this value.
+ */
+#define kMaxPictureOpsToUnrollInsteadOfRef  1
 
 void SkCanvas::drawPicture(const SkPicture* picture, const SkMatrix* matrix, const SkPaint* paint) {
-    TRACE_EVENT0("disabled-by-default-skia", "SkCanvas::drawPicture(SkMatrix, SkPaint)");
+    TRACE_EVENT0("disabled-by-default-skia", "SkCanvas::drawPicture()");
     if (picture) {
         if (matrix && matrix->isIdentity()) {
             matrix = NULL;
         }
-        this->onDrawPicture(picture, matrix, paint);
+        if (picture->approximateOpCount() <= kMaxPictureOpsToUnrollInsteadOfRef) {
+            SkAutoCanvasMatrixPaint acmp(this, matrix, paint, picture->cullRect());
+            picture->playback(this);
+        } else {
+            this->onDrawPicture(picture, matrix, paint);
+        }
     }
 }
 
 void SkCanvas::onDrawPicture(const SkPicture* picture, const SkMatrix* matrix,
                              const SkPaint* paint) {
     SkBaseDevice* device = this->getTopDevice();
     if (device) {
         // Canvas has to first give the device the opportunity to render
         // the picture itself.
         if (device->EXPERIMENTAL_drawPicture(this, picture, matrix, paint)) {
             return; // the device has rendered the entire picture
         }
     }
 
     SkAutoCanvasMatrixPaint acmp(this, matrix, paint, picture->cullRect());
-
     picture->playback(this);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////////////////////////
 
 SkCanvas::LayerIter::LayerIter(SkCanvas* canvas, bool skipEmptyClips) {
     SK_COMPILE_ASSERT(sizeof(fStorage) >= sizeof(SkDrawIter), fStorage_too_small);
 
     SkASSERT(canvas);
@@ skipping 87 matching lines @@
     }
 
     if (matrix) {
         canvas->concat(*matrix);
     }
 }
 
 SkAutoCanvasMatrixPaint::~SkAutoCanvasMatrixPaint() {
     fCanvas->restoreToCount(fSaveCount);
 }