Allow explicit conversion operators and implement WTF::OwnPtr::operator bool.

third_party/WebKit/Source/core/animation/InterpolationValue.h

Index: third_party/WebKit/Source/core/animation/InterpolationValue.h
diff --git a/third_party/WebKit/Source/core/animation/InterpolationValue.h b/third_party/WebKit/Source/core/animation/InterpolationValue.h
index cf73188c81e67d0d059361100800a4b5c8447565..2b585ec173d392a636a5ec0f9a271bbff2aea17c 100644
--- a/third_party/WebKit/Source/core/animation/InterpolationValue.h
+++ b/third_party/WebKit/Source/core/animation/InterpolationValue.h
@@ -34,7 +34,7 @@ struct InterpolationValue {
         nonInterpolableValue = other.nonInterpolableValue.release();
     }
 
-    operator bool() const { return interpolableValue; }
+    operator bool() const { return !!interpolableValue; }

[Nico, 2016/04/13 01:19:01]

bleh, i hate that !! pattern. can we static_cast<bool> instead?

[alancutter (OOO until 2018), 2016/04/13 02:26:32]

I dislike !! as well but static_cast<bool> is also undesirable.
I think the practice should be to use .get() instead.

[jbroman, 2016/04/13 13:38:09]

I actually don't mind !!, but static_cast<bool>(pointer) is super verbose. I'm
okay with pointer.get() and relying on the implicit bool conversion there. I
also prefer "pointer != nullptr" (which, amusingly, check-webkit-style actually
rejects) and "bool{pointer}" to static_cast<bool>.

Since .get() seems to be okay with everyone who's weighed in so far, I've
changed to that.

 
     InterpolationValue clone() const
     {