Throw exception on null pointers in raw toNative

Throw exception on null pointers in raw toNative

Currently, all of the different variants of toNative will
 convert a Dart_Null to a null pointer without throwing an
 error.  This is incorrect: for non nullable types, many of
 the underlying blink implementations will crash if given a
 null pointer (see for example https://code.google.com/p/dart/issues/detail?id=19948).
 This CL is a first cut a correcting this.  I've changed
the template generator for the wrappers to produce code
which throws an error if given Dart_Null in the non
WithNullCheck cases.  I think this code should actually be
substantially refactored - the naming convention is quite
confusing at the moment - but for the time being this
addresses the immediate bug and makes things less likely to
 crash on bad inputs.  Some custom code had to be updated
 to use toNativeWithNullCheck (corresponding to
toNativeWithTypeCheck in the V8 case).

BUG=http://dartbug.com/19948
R=vsm@google.com

Committed: https://src.chromium.org/viewvc/blink/branches/dart/dartium?view=rev&revision=180097

[vsm, 2014-08-12 08:19:22]

lgtm

Agreed on confusing names.  Perhaps toNative should be toNativeThrowOnNull?

Do you notice / expect any perf difference?

[Leaf, 2014-08-12 16:47:08]

On 2014/08/12 08:19:22, vsm wrote:
> lgtm
> 
> Agreed on confusing names.  Perhaps toNative should be toNativeThrowOnNull?
> 
> Do you notice / expect any perf difference?

I haven't measured for performance, might try to give it a run before I submit. 
Most of the paths should either improve or have negligible performance change,
but the version of toNative which takes a Dart_Handle does an extra IsNull check
which would have a performance effect.  With some refactoring this IsNull check
should be eliminable (since it is being done redundantly) but I don't think I
have time to do this properly for 1.6 - would prefer to follow up with another
CL to re-organize all of this.  I'll work on coming up with some design ideas
for how to organize this code nicely.

[Leaf, 2014-08-12 19:47:40]

Committed patchset #1 manually as 180097 (presubmit successful).