Fix crash when the OfflineAudioContext constructor is given 0 as numberOfFrames

Source/modules/webaudio/AudioContext.cpp

Index: Source/modules/webaudio/AudioContext.cpp
diff --git a/Source/modules/webaudio/AudioContext.cpp b/Source/modules/webaudio/AudioContext.cpp
index fb7d57ef55602524189f2cbec2740afddcc99c6b..18f3df70c123b647cef8ebce9c03949c378cb840 100644
--- a/Source/modules/webaudio/AudioContext.cpp
+++ b/Source/modules/webaudio/AudioContext.cpp
@@ -154,7 +154,9 @@ AudioContext::AudioContext(Document* document, unsigned numberOfChannels, size_t
 
     // Create a new destination for offline rendering.
     m_renderTarget = AudioBuffer::create(numberOfChannels, numberOfFrames, sampleRate);
+    ASSERT(m_renderTarget);
     m_destinationNode = OfflineAudioDestinationNode::create(this, m_renderTarget.get());
+    ASSERT(m_destinationNode);

[Raymond Toy (Google), 2013/10/11 20:04:40]

Did these two asserts catch the crash?

I'm just concerned that debug code will find this, but release code will not and
crash in some strange place.

It would be nice if we threw an error in these cases too.

[Inactive, 2013/10/11 20:14:30]

Yes, these assertions would have caught the crash. The issue was that
AudioBuffer::create() would fail due to bad input and return 0.
Then the OfflineAudioDestinationNode constructor would try the use the null
renderTarget.

It is up to the factory methods to validate the input properly so that the
constructor does not fail. I think those assertion are useful indicators that
the factory did not validate properly. We cannot throw js exceptions here, they
should be thrown earlier in the factory.

 }
 
 void AudioContext::constructCommon()