clarify that accessPixels is for write-access, and peekPixels is RO

src/core/SkBitmapDevice.cpp

Index: src/core/SkBitmapDevice.cpp
diff --git a/src/core/SkBitmapDevice.cpp b/src/core/SkBitmapDevice.cpp
index 2a805cbf02bd1e77b081fd14d2e0a5f0f324924f..343bbc8893a814a4dec83ea4375ec7a9671c80bb 100644
--- a/src/core/SkBitmapDevice.cpp
+++ b/src/core/SkBitmapDevice.cpp
@@ -126,7 +126,11 @@ const SkBitmap& SkBitmapDevice::onAccessBitmap() {
 }
 
 bool SkBitmapDevice::onAccessPixels(SkPixmap* pmap) {
-    return fBitmap.lockPixelsAreWritable() && this->onPeekPixels(pmap);
+    if (fBitmap.lockPixelsAreWritable() && this->onPeekPixels(pmap)) {
+        fBitmap.notifyPixelsChanged();
+        return true;
+    }
+    return false;
 }
 
 bool SkBitmapDevice::onPeekPixels(SkPixmap* pmap) {