Send a PluginDocument's data directly to the PluginView from PluginDocument,
rather than sending it via FrameLoaderClientImpl.

Remove some now unnecessary FrameLoaderClient callbacks and simplify
DocumentLoader and FrameLoaderClientImpl

BUG=none

Review URL: https://chromiumcodereview.appspot.com/17155025

git-svn-id: svn://svn.chromium.org/blink/trunk@153087 bbb929c8-8fbe-4397-9dbb-9b2b20218538