Disable assertion of fBoundsIsDirty.

We allow this to be raced on, and it may have already become not-dirty by the
time we get to this function if computed by another thread.

BUG=skia:

Review URL: https://codereview.chromium.org/398913002

include/core/SkPathRef.h

diff --git a/include/core/SkPathRef.h b/include/core/SkPathRef.h
index ed7c317..ba68fcb 100644
--- a/include/core/SkPathRef.h
+++ b/include/core/SkPathRef.h
@@ -291,7 +291,9 @@
     // called, if dirty, by getBounds()
     void computeBounds() const {
         SkDEBUGCODE(this->validate();)
-        SkASSERT(fBoundsIsDirty);
+        // TODO(mtklein): remove fBoundsIsDirty and fIsFinite,
+        // using an inverted rect instead of fBoundsIsDirty and always recalculating fIsFinite.
+        //SkASSERT(fBoundsIsDirty);
 
         fIsFinite = ComputePtBounds(fBounds.get(), *this);
         fBoundsIsDirty = false;