PeriodicWave returns sine wave generator if no coefficients given

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

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 81 matching lines @@
                 imag->data(), disableNormalization, exceptionState);
 }
 
 PeriodicWave* PeriodicWave::create(BaseAudioContext* context,
                                    const PeriodicWaveOptions& options,
                                    ExceptionState& exceptionState) {
   bool normalize = options.hasDisableNormalization()
                        ? options.disableNormalization()
                        : false;
 
-  if (!options.hasReal() && !options.hasImag()) {
-    exceptionState.throwDOMException(
-        InvalidStateError,
-        "At least one of real and imag members must be specified.");
-    return nullptr;
-  }
-
   Vector<float> realCoef;
   Vector<float> imagCoef;
 
   if (options.hasReal()) {
     realCoef = options.real();
     if (options.hasImag())
       imagCoef = options.imag();
     else
       imagCoef.resize(realCoef.size());
-  } else {
-    // We know real is not given, so imag must exist (because we checked for
-    // this above).
+  } else if (options.hasImag()) {
+    // |real| not given, but we have |imag|.
     imagCoef = options.imag();
     realCoef.resize(imagCoef.size());
+  } else {
+    // Neither |real| nor |imag| given.  Return an object that would
+    // generate a sine wave, which means real = [0,0], and imag = [0, 1]
+    realCoef.resize(2);
+    imagCoef.resize(2);
+    imagCoef[1] = 1;
   }
 
   return create(*context, realCoef.size(), realCoef.data(), imagCoef.size(),
                 imagCoef.data(), normalize, exceptionState);
 }
 
 PeriodicWave* PeriodicWave::createSine(float sampleRate) {
   PeriodicWave* periodicWave = new PeriodicWave(sampleRate);
   periodicWave->generateBasicWaveform(OscillatorHandler::SINE);
   return periodicWave;
@@ skipping 264 matching lines @@
     }
 
     realP[n] = 0;
     imagP[n] = b;
   }
 
   createBandLimitedTables(realP, imagP, halfSize, false);
 }
 
 }  // namespace blink