Move members of HTMLPlugInImageElement to HTMLPlugInElement, part 4.

This CL moves the following member functions:
 - allowedToLoadFrameURL()
 - wouldLoadAsNetscapePlugin()
 - createRenderer()
 - willRecalcStyle()
 - finishParsingChildren()

Note: We should move setHasCustomStyleCallbacks() call in the constructor
for willRecalcStyle().

Also, this CL remove member functions without implementations,
swapRendererTimerFired() and restartSimilarPlugIns().

This is a part of a task to merge HTMLPlugInImageELement into HTMLPlugInElement.
Only HTMLPlugInImageElement inherits from HTMLPlugInElement.

BUG=309978

Review URL: https://codereview.chromium.org/38453002

git-svn-id: svn://svn.chromium.org/blink/trunk@160401 bbb929c8-8fbe-4397-9dbb-9b2b20218538