writepixels needs to bump genID

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index ec98b7e3e63c3059f4d1983ec4ac107cb1193fa1..2fb5c951249d54c1905107e0a1c6161e1461281a 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -753,6 +753,9 @@ bool SkCanvas::writePixels(const SkImageInfo& origInfo, const void* pixels, size
     // here x,y are either 0 or negative
     pixels = ((const char*)pixels - y * rowBytes - x * info.bytesPerPixel());
 
+    // Tell our owning surface to bump its generation ID
+    this->predrawNotify();
+
     // The device can assert that the requested area is always contained in its bounds
     return device->writePixels(info, pixels, rowBytes, target.x(), target.y());
 }