Don't move raw pointers in SkCanvas

Moving raw pointers does the same job as copying, but is more verbose and also
more confusing: e.g., is the supposed pointer meant to be a smart one?

This instance was flagged by the tool from
https://codereview.chromium.org/2919243002/.

BUG=chromium:729393

Change-Id: I4c89e9d80fab9f6d14ab7db53e8b9b6e7cf966dc
Reviewed-on: https://skia-review.googlesource.com/18540
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>

include/core/SkCanvas.h

@@ -345,7 +345,7 @@ public:
             : fBounds(bounds)
             , fPaint(paint)
             , fBackdrop(backdrop)
-            , fClipMask(std::move(clipMask))
+            , fClipMask(clipMask)
             , fClipMatrix(clipMatrix)
             , fSaveLayerFlags(saveLayerFlags)
         {}