Drop [LegacyInterfaceTypeChecking] where trivial in Web Audio

third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.cpp

Index: third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.cpp
index 9b627c3fd9f540e636430a9b9931115bafceecf0..6490741d7cacccbd52a5a4a1752800944b8bf2a7 100644
--- a/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.cpp
@@ -198,12 +198,6 @@ void AbstractAudioContext::decodeAudioData(DOMArrayBuffer* audioData, AudioBuffe
         return;
     }
 
-    if (!audioData) {
-        exceptionState.throwDOMException(
-            SyntaxError,
-            "invalid ArrayBuffer for audioData.");
-        return;
-    }
     m_audioDecoder.decodeAsync(audioData, sampleRate(), successCallback, errorCallback);
 }
 
@@ -233,13 +227,6 @@ MediaElementAudioSourceNode* AbstractAudioContext::createMediaElementSource(HTML
         return nullptr;
     }
 
-    if (!mediaElement) {
-        exceptionState.throwDOMException(
-            InvalidStateError,
-            "invalid HTMLMedialElement.");
-        return nullptr;
-    }
-
     // First check if this media element already has a source node.
     if (mediaElement->audioSourceNode()) {
         exceptionState.throwDOMException(
@@ -265,13 +252,6 @@ MediaStreamAudioSourceNode* AbstractAudioContext::createMediaStreamSource(MediaS
         return nullptr;
     }
 
-    if (!mediaStream) {
-        exceptionState.throwDOMException(
-            InvalidStateError,
-            "invalid MediaStream source");
-        return nullptr;
-    }
-
     MediaStreamTrackVector audioTracks = mediaStream->getAudioTracks();
     if (audioTracks.isEmpty()) {
         exceptionState.throwDOMException(
@@ -558,20 +538,6 @@ PeriodicWave* AbstractAudioContext::createPeriodicWave(DOMFloat32Array* real, DO
         return nullptr;
     }
 
-    if (!real) {
-        exceptionState.throwDOMException(
-            SyntaxError,
-            "invalid real array");
-        return nullptr;
-    }
-
-    if (!imag) {
-        exceptionState.throwDOMException(
-            SyntaxError,
-            "invalid imaginary array");
-        return nullptr;
-    }
-
     if (real->length() != imag->length()) {
         exceptionState.throwDOMException(
             IndexSizeError,