PVS-Studio warning V519 for WebKit

static v8::Handle<v8::Value>
toV8Object(....)
{
  switch (extension->name()) {
    ....
    case WebGLExtension::WebGLCompressedTextureATCName:
      extensionObject = toV8(....);
      referenceName = "webGLCompressedTextureATCName";
    case WebGLExtension::WebGLCompressedTexturePVRTCName:
      extensionObject = toV8(....);
      referenceName = "webGLCompressedTexturePVRTCName";
      break;
  }
  ....
}

This suspicious code was found in WebKit project by PVS-Studio static code analyzer.
Warning message is:
V519 The 'extensionObject' variable is assigned values twice successively. Perhaps this is a mistake. Check lines: 222, 225. V8WebGLRenderingContextCustom.cpp 225

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/