Fix up the clip mask manager's creation of paths (w.r.t. volatility)

I don't expect this to make any difference (perf-wise) but it seems more correct.

This CL relies on https://codereview.chromium.org/1421533007/ (Fix ClipMaskManager's SW-fallback logic)

Committed: https://skia.googlesource.com/skia/+/953fe3139fa60ce56abcfa45a3647d924e637083

Review URL: https://codereview.chromium.org/1419403002
diff --git a/src/core/SkClipStack.cpp b/src/core/SkClipStack.cpp
index f54d57f..4227eea 100644
--- a/src/core/SkClipStack.cpp
+++ b/src/core/SkClipStack.cpp
@@ -136,14 +136,17 @@
     switch (fType) {
         case kEmpty_Type:
             path->reset();
+            path->setIsVolatile(true);
             break;
         case kRect_Type:
             path->reset();
             path->addRect(this->getRect());
+            path->setIsVolatile(true);
             break;
         case kRRect_Type:
             path->reset();
             path->addRRect(fRRect);
+            path->setIsVolatile(true);
             break;
         case kPath_Type:
             *path = *fPath.get();