Add MultiPictureDraw to nanobench

src/core/SkBitmap.cpp

Index: src/core/SkBitmap.cpp
diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index f0ad029bea9285b74f03bbb0700ad09d1255c797..836825db24afcb0cc417aa175fd792d9b43a2271 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -1323,7 +1323,6 @@ void SkBitmap::validate() const {
 
     if (fPixels) {
         SkASSERT(fPixelRef);

[robertphillips, 2014/11/21 13:18:35]

In a multithreaded world this bitmap's unlockPixels method can be called on this
bitmap between the 'fPixels' check and here so, 'fPixelLockCount' can be zero.

[mtklein, 2014/11/21 13:40:44]

Not lgtm

This seems important for correctness.  Isn't the issue SkBitmaps are just not
threadafe?  We've always copied them before use... Did we miss a spot?

If you like, let's revert this, reland the original cl without threading, and
I'll follow up on turning it on.  Don't want to block getting mpd running.

-        SkASSERT(fPixelLockCount > 0);
         SkASSERT(fPixelRef->isLocked());
         SkASSERT(fPixelRef->rowBytes() == fRowBytes);
         SkASSERT(fPixelRefOrigin.fX >= 0);