IndexedDB: Simplify blink public/platform implementation names

Following the move of the IndexedDB backend from Blink to Chromium,
the implementations of the WebIDB${FOO} types from the Blink
public/platform API are no longer proxies for objects elsewhere in the
system. Simplify the file and class names appropriately.

proxy_webidb${FOO}_impl.{cc,h} => webidb${FOO}_impl.{cc,h}
RendererWebIDB${FOO}Impl => WebIDB{$FOO}Impl
... and git-cl format FTW!

R=jam

Review URL: https://codereview.chromium.org/100503005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240256 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240256